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 $86.86   10.450%   $95.9369   $95.94   $95.95   $95.90  
  Purchase #2 $126.82   7.511%   $136.3455   $136.35   $136.35   $136.30  
  Purchase #3 $111.43   4.667%   $116.6304   $116.63   $116.65   $116.60  
  Purchase #4 $16.37   13.265%   $18.5415   $18.54   $18.55   $18.50  
  Purchase #5 $135.96   8.693%   $147.779   $147.78   $147.80   $147.80  
  Purchase #6 $146.63   11.495%   $163.4851   $163.49   $163.50   $163.50  
  Purchase #7 $212.87   6.779%   $227.3005   $227.30   $227.30   $227.30  
  7 purchase totals = $836.94       $906.0189   $906.03   $906.10   $905.90