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 $84.67   13.299%   $95.9303   $95.93   $95.95   $95.90  
  Purchase #2 $34.63   4.592%   $36.2202   $36.22   $36.20   $36.20  
  Purchase #3 $144.88   12.243%   $162.6177   $162.62   $162.60   $162.60  
  Purchase #4 $61.61   10.829%   $68.2817   $68.28   $68.30   $68.30  
  Purchase #5 $166.59   5.311%   $175.4376   $175.44   $175.45   $175.40  
  Purchase #6 $181.78   11.336%   $202.3866   $202.39   $202.40   $202.40  
  Purchase #7 $39.63   13.555%   $45.0018   $45.00   $45.00   $45.00  
  7 purchase totals = $713.79       $785.8759   $785.88   $785.90   $785.80