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 $87.69   8.567%   $95.2024   $95.20   $95.20   $95.20  
  Purchase #2 $193.28   12.306%   $217.065   $217.07   $217.05   $217.10  
  Purchase #3 $139.25   7.197%   $149.2718   $149.27   $149.25   $149.30  
  Purchase #4 $188.94   3.187%   $194.9615   $194.96   $194.95   $195.00  
  Purchase #5 $68.71   7.502%   $73.8646   $73.86   $73.85   $73.90  
  Purchase #6 $227.70   11.735%   $254.4206   $254.42   $254.40   $254.40  
  Purchase #7 $249.49   4.196%   $259.9586   $259.96   $259.95   $260.00  
  7 purchase totals = $1,155.06       $1,244.7445   $1,244.74   $1,244.65   $1,244.90