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 $211.90   8.517%   $229.9475   $229.95   $229.95   $229.90  
  Purchase #2 $48.52   13.345%   $54.995   $55.00   $55.00   $55.00  
  Purchase #3 $135.49   11.497%   $151.0673   $151.07   $151.05   $151.10  
  Purchase #4 $68.96   11.312%   $76.7608   $76.76   $76.75   $76.80  
  Purchase #5 $244.26   7.229%   $261.9176   $261.92   $261.90   $261.90  
  Purchase #6 $233.38   3.699%   $242.0127   $242.01   $242.00   $242.00  
  Purchase #7 $182.87   9.795%   $200.7821   $200.78   $200.80   $200.80  
  7 purchase totals = $1,125.38       $1,217.4830   $1,217.49   $1,217.45   $1,217.50