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 $171.45   7.352%   $184.055   $184.06   $184.05   $184.10  
  Purchase #2 $59.90   3.437%   $61.9588   $61.96   $61.95   $62.00  
  Purchase #3 $51.51   4.682%   $53.9217   $53.92   $53.90   $53.90  
  Purchase #4 $167.74   4.828%   $175.8385   $175.84   $175.85   $175.80  
  Purchase #5 $209.56   12.726%   $236.2286   $236.23   $236.25   $236.20  
  Purchase #6 $245.73   5.657%   $259.6309   $259.63   $259.65   $259.60  
  Purchase #7 $135.83   13.389%   $154.0163   $154.02   $154.00   $154.00  
  7 purchase totals = $1,041.72       $1,125.6498   $1,125.66   $1,125.65   $1,125.60