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 $90.57   4.367%   $94.5252   $94.53   $94.55   $94.50  
  Purchase #2 $215.37   6.372%   $229.0934   $229.09   $229.10   $229.10  
  Purchase #3 $207.30   4.259%   $216.1289   $216.13   $216.15   $216.10  
  Purchase #4 $84.28   4.435%   $88.0178   $88.02   $88.00   $88.00  
  Purchase #5 $250.71   4.259%   $261.3877   $261.39   $261.40   $261.40  
  Purchase #6 $149.79   5.262%   $157.6719   $157.67   $157.65   $157.70  
  Purchase #7 $194.36   9.713%   $213.2382   $213.24   $213.25   $213.20  
  7 purchase totals = $1,192.38       $1,260.0631   $1,260.07   $1,260.10   $1,260.00