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 $113.95   4.484%   $119.0595   $119.06   $119.05   $119.10  
  Purchase #2 $67.75   9.745%   $74.3522   $74.35   $74.35   $74.40  
  Purchase #3 $5.78   7.612%   $6.22   $6.22   $6.20   $6.20  
  Purchase #4 $219.83   8.367%   $238.2232   $238.22   $238.20   $238.20  
  Purchase #5 $116.43   8.324%   $126.1216   $126.12   $126.10   $126.10  
  Purchase #6 $136.71   12.280%   $153.498   $153.50   $153.50   $153.50  
  Purchase #7 $39.45   9.411%   $43.1626   $43.16   $43.15   $43.20  
  7 purchase totals = $699.90       $760.6371   $760.63   $760.55   $760.70