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 $119.87   4.298%   $125.022   $125.02   $125.00   $125.00  
  Purchase #2 $170.42   9.506%   $186.6201   $186.62   $186.60   $186.60  
  Purchase #3 $233.40   12.508%   $262.5937   $262.59   $262.60   $262.60  
  Purchase #4 $207.44   6.633%   $221.1995   $221.20   $221.20   $221.20  
  Purchase #5 $91.46   11.865%   $102.3117   $102.31   $102.30   $102.30  
  Purchase #6 $232.56   3.703%   $241.1717   $241.17   $241.15   $241.20  
  Purchase #7 $207.91   9.578%   $227.8236   $227.82   $227.80   $227.80  
  7 purchase totals = $1,263.06       $1,366.7423   $1,366.73   $1,366.65   $1,366.70