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 $228.58   7.598%   $245.9475   $245.95   $245.95   $245.90  
  Purchase #2 $232.55   5.729%   $245.8728   $245.87   $245.85   $245.90  
  Purchase #3 $160.73   9.354%   $175.7647   $175.76   $175.75   $175.80  
  Purchase #4 $101.82   8.159%   $110.1275   $110.13   $110.15   $110.10  
  Purchase #5 $52.49   3.833%   $54.5019   $54.50   $54.50   $54.50  
  Purchase #6 $245.83   11.535%   $274.1865   $274.19   $274.20   $274.20  
  Purchase #7 $216.26   4.701%   $226.4264   $226.43   $226.45   $226.40  
  7 purchase totals = $1,238.26       $1,332.8273   $1,332.83   $1,332.85   $1,332.80