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 $174.71   13.131%   $197.6512   $197.65   $197.65   $197.70  
  Purchase #2 $170.35   13.286%   $192.9827   $192.98   $193.00   $193.00  
  Purchase #3 $64.52   13.448%   $73.1966   $73.20   $73.20   $73.20  
  Purchase #4 $242.66   7.246%   $260.2431   $260.24   $260.25   $260.20  
  Purchase #5 $38.69   13.683%   $43.984   $43.98   $44.00   $44.00  
  Purchase #6 $241.98   8.364%   $262.2192   $262.22   $262.20   $262.20  
  Purchase #7 $156.37   8.682%   $169.946   $169.95   $169.95   $169.90  
  7 purchase totals = $1,089.28       $1,200.2228   $1,200.22   $1,200.25   $1,200.20