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 $215.95   6.473%   $229.9284   $229.93   $229.95   $229.90  
  Purchase #2 $211.77   11.466%   $236.0515   $236.05   $236.05   $236.10  
  Purchase #3 $202.53   6.745%   $216.1906   $216.19   $216.20   $216.20  
  Purchase #4 $229.53   3.859%   $238.3876   $238.39   $238.40   $238.40  
  Purchase #5 $94.68   3.730%   $98.2116   $98.21   $98.20   $98.20  
  Purchase #6 $43.60   5.392%   $45.9509   $45.95   $45.95   $46.00  
  Purchase #7 $46.41   9.848%   $50.9805   $50.98   $51.00   $51.00  
  7 purchase totals = $1,044.47       $1,115.7011   $1,115.70   $1,115.75   $1,115.80