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 $144.51   5.355%   $152.2485   $152.25   $152.25   $152.20  
  Purchase #2 $70.39   10.283%   $77.6282   $77.63   $77.65   $77.60  
  Purchase #3 $89.34   13.628%   $101.5153   $101.52   $101.50   $101.50  
  Purchase #4 $95.82   7.106%   $102.629   $102.63   $102.65   $102.60  
  Purchase #5 $154.55   7.644%   $166.3638   $166.36   $166.35   $166.40  
  Purchase #6 $61.64   8.128%   $66.6501   $66.65   $66.65   $66.70  
  Purchase #7 $121.30   4.167%   $126.3546   $126.35   $126.35   $126.40  
  7 purchase totals = $737.55       $793.3895   $793.39   $793.40   $793.40