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 $71.32   7.355%   $76.5656   $76.57   $76.55   $76.60  
  Purchase #2 $39.76   13.491%   $45.124   $45.12   $45.10   $45.10  
  Purchase #3 $29.90   12.361%   $33.5959   $33.60   $33.60   $33.60  
  Purchase #4 $63.99   7.182%   $68.5858   $68.59   $68.60   $68.60  
  Purchase #5 $199.82   7.774%   $215.354   $215.35   $215.35   $215.40  
  Purchase #6 $168.32   11.756%   $188.1077   $188.11   $188.10   $188.10  
  Purchase #7 $126.62   10.383%   $139.767   $139.77   $139.75   $139.80  
  7 purchase totals = $699.73       $767.1000   $767.11   $767.05   $767.20