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 $70.95   8.486%   $76.9708   $76.97   $76.95   $77.00  
  Purchase #2 $35.84   5.167%   $37.6919   $37.69   $37.70   $37.70  
  Purchase #3 $118.76   6.511%   $126.4925   $126.49   $126.50   $126.50  
  Purchase #4 $244.38   9.443%   $267.4568   $267.46   $267.45   $267.50  
  Purchase #5 $86.50   9.223%   $94.4779   $94.48   $94.50   $94.50  
  Purchase #6 $207.26   10.756%   $229.5529   $229.55   $229.55   $229.60  
  Purchase #7 $145.42   10.482%   $160.6629   $160.66   $160.65   $160.70  
  7 purchase totals = $909.11       $993.3057   $993.30   $993.30   $993.50