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 $207.28   9.488%   $226.9467   $226.95   $226.95   $226.90  
  Purchase #2 $54.92   8.122%   $59.3806   $59.38   $59.40   $59.40  
  Purchase #3 $155.34   9.539%   $170.1579   $170.16   $170.15   $170.20  
  Purchase #4 $30.63   8.702%   $33.2954   $33.30   $33.30   $33.30  
  Purchase #5 $249.77   12.710%   $281.5158   $281.52   $281.50   $281.50  
  Purchase #6 $126.55   7.616%   $136.188   $136.19   $136.20   $136.20  
  Purchase #7 $200.88   7.455%   $215.8556   $215.86   $215.85   $215.90  
  7 purchase totals = $1,025.37       $1,123.3400   $1,123.36   $1,123.35   $1,123.40