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 $60.62   12.186%   $68.0072   $68.01   $68.00   $68.00  
  Purchase #2 $53.81   13.265%   $60.9479   $60.95   $60.95   $60.90  
  Purchase #3 $169.76   10.146%   $186.9838   $186.98   $187.00   $187.00  
  Purchase #4 $26.56   5.295%   $27.9664   $27.97   $27.95   $28.00  
  Purchase #5 $202.78   5.159%   $213.2414   $213.24   $213.25   $213.20  
  Purchase #6 $234.67   12.671%   $264.405   $264.41   $264.40   $264.40  
  Purchase #7 $125.76   6.546%   $133.9922   $133.99   $134.00   $134.00  
  7 purchase totals = $873.96       $955.5439   $955.55   $955.55   $955.50