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 $216.98   5.197%   $228.2565   $228.26   $228.25   $228.30  
  Purchase #2 $52.43   11.572%   $58.4972   $58.50   $58.50   $58.50  
  Purchase #3 $183.59   4.109%   $191.1337   $191.13   $191.15   $191.10  
  Purchase #4 $43.93   6.201%   $46.6541   $46.65   $46.65   $46.70  
  Purchase #5 $25.78   9.485%   $28.2252   $28.23   $28.25   $28.20  
  Purchase #6 $235.48   4.228%   $245.4361   $245.44   $245.45   $245.40  
  Purchase #7 $196.39   9.689%   $215.4182   $215.42   $215.40   $215.40  
  7 purchase totals = $954.58       $1,013.6210   $1,013.63   $1,013.65   $1,013.60