Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $169.32   10.409%   $186.9445   $186.94   $186.95   $186.90  
  Purchase #2 $176.91   10.370%   $195.2556   $195.26   $195.25   $195.30  
  Purchase #3 $201.56   3.478%   $208.5703   $208.57   $208.55   $208.60  
  Purchase #4 $179.46   10.482%   $198.271   $198.27   $198.25   $198.30  
  Purchase #5 $192.85   12.382%   $216.7287   $216.73   $216.75   $216.70  
  Purchase #6 $150.75   5.154%   $158.5197   $158.52   $158.50   $158.50  
  Purchase #7 $167.43   10.116%   $184.3672   $184.37   $184.35   $184.40  
  7 purchase totals = $1,238.28       $1,348.6570   $1,348.66   $1,348.60   $1,348.70