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 $175.95   13.802%   $200.2346   $200.23   $200.25   $200.20  
  Purchase #2 $151.92   4.427%   $158.6455   $158.65   $158.65   $158.60  
  Purchase #3 $91.54   4.342%   $95.5147   $95.51   $95.50   $95.50  
  Purchase #4 $224.85   5.670%   $237.599   $237.60   $237.60   $237.60  
  Purchase #5 $220.27   6.711%   $235.0523   $235.05   $235.05   $235.10  
  Purchase #6 $249.47   10.234%   $275.0008   $275.00   $275.00   $275.00  
  Purchase #7 $12.47   13.772%   $14.1874   $14.19   $14.20   $14.20  
  7 purchase totals = $1,126.47       $1,216.2343   $1,216.23   $1,216.25   $1,216.20