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 $168.99   3.662%   $175.1784   $175.18   $175.20   $175.20  
  Purchase #2 $238.96   11.442%   $266.3018   $266.30   $266.30   $266.30  
  Purchase #3 $229.50   3.111%   $236.6397   $236.64   $236.65   $236.60  
  Purchase #4 $174.31   11.333%   $194.0646   $194.06   $194.05   $194.10  
  Purchase #5 $230.98   13.215%   $261.504   $261.50   $261.50   $261.50  
  Purchase #6 $33.25   8.161%   $35.9635   $35.96   $35.95   $36.00  
  Purchase #7 $83.80   8.566%   $90.9783   $90.98   $91.00   $91.00  
  7 purchase totals = $1,159.79       $1,260.6303   $1,260.62   $1,260.65   $1,260.70