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 $68.95   10.151%   $75.9491   $75.95   $75.95   $75.90  
  Purchase #2 $86.39   8.775%   $93.9707   $93.97   $93.95   $94.00  
  Purchase #3 $125.52   3.615%   $130.0575   $130.06   $130.05   $130.10  
  Purchase #4 $120.71   13.276%   $136.7355   $136.74   $136.75   $136.70  
  Purchase #5 $154.65   4.228%   $161.1886   $161.19   $161.20   $161.20  
  Purchase #6 $140.69   11.146%   $156.3713   $156.37   $156.35   $156.40  
  Purchase #7 $127.44   6.774%   $136.0728   $136.07   $136.05   $136.10  
  7 purchase totals = $824.35       $890.3455   $890.35   $890.30   $890.40