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 $96.94   10.639%   $107.2534   $107.25   $107.25   $107.30  
  Purchase #2 $185.50   4.557%   $193.9532   $193.95   $193.95   $194.00  
  Purchase #3 $163.50   8.248%   $176.9855   $176.99   $177.00   $177.00  
  Purchase #4 $161.62   8.247%   $174.9488   $174.95   $174.95   $174.90  
  Purchase #5 $212.55   4.279%   $221.645   $221.65   $221.65   $221.60  
  Purchase #6 $200.43   5.307%   $211.0668   $211.07   $211.05   $211.10  
  Purchase #7 $107.74   10.168%   $118.695   $118.70   $118.70   $118.70  
  7 purchase totals = $1,128.28       $1,204.5477   $1,204.56   $1,204.55   $1,204.60