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 $86.83   8.745%   $94.4233   $94.42   $94.40   $94.40  
  Purchase #2 $89.43   5.828%   $94.642   $94.64   $94.65   $94.60  
  Purchase #3 $168.49   11.165%   $187.3019   $187.30   $187.30   $187.30  
  Purchase #4 $89.95   10.809%   $99.6727   $99.67   $99.65   $99.70  
  Purchase #5 $34.71   8.315%   $37.5961   $37.60   $37.60   $37.60  
  Purchase #6 $118.44   6.476%   $126.1102   $126.11   $126.10   $126.10  
  Purchase #7 $64.96   5.528%   $68.551   $68.55   $68.55   $68.60  
  7 purchase totals = $652.81       $708.2972   $708.29   $708.25   $708.30