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 $67.29   13.113%   $76.1137   $76.11   $76.10   $76.10  
  Purchase #2 $122.75   7.361%   $131.7856   $131.79   $131.80   $131.80  
  Purchase #3 $6.71   3.466%   $6.9426   $6.94   $6.95   $6.90  
  Purchase #4 $99.68   11.339%   $110.9827   $110.98   $111.00   $111.00  
  Purchase #5 $52.44   9.222%   $57.276   $57.28   $57.30   $57.30  
  Purchase #6 $180.86   7.555%   $194.524   $194.52   $194.50   $194.50  
  Purchase #7 $164.52   11.302%   $183.1141   $183.11   $183.10   $183.10  
  7 purchase totals = $694.25       $760.7387   $760.73   $760.75   $760.70