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 $59.68   5.726%   $63.0973   $63.10   $63.10   $63.10  
  Purchase #2 $148.43   12.651%   $167.2079   $167.21   $167.20   $167.20  
  Purchase #3 $61.30   12.437%   $68.9239   $68.92   $68.90   $68.90  
  Purchase #4 $134.47   12.730%   $151.588   $151.59   $151.60   $151.60  
  Purchase #5 $20.39   8.468%   $22.1166   $22.12   $22.10   $22.10  
  Purchase #6 $199.38   5.521%   $210.3878   $210.39   $210.40   $210.40  
  Purchase #7 $189.81   7.821%   $204.655   $204.66   $204.65   $204.70  
  7 purchase totals = $813.46       $887.9765   $887.99   $887.95   $888.00