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 $114.28   3.339%   $118.0958   $118.10   $118.10   $118.10  
  Purchase #2 $216.46   11.731%   $241.8529   $241.85   $241.85   $241.90  
  Purchase #3 $221.77   10.619%   $245.3198   $245.32   $245.30   $245.30  
  Purchase #4 $219.46   10.413%   $242.3124   $242.31   $242.30   $242.30  
  Purchase #5 $242.63   5.591%   $256.1954   $256.20   $256.20   $256.20  
  Purchase #6 $250.61   11.590%   $279.6557   $279.66   $279.65   $279.70  
  Purchase #7 $204.60   6.392%   $217.678   $217.68   $217.70   $217.70  
  7 purchase totals = $1,469.81       $1,601.1100   $1,601.12   $1,601.10   $1,601.20