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 $182.50   6.708%   $194.7421   $194.74   $194.75   $194.70  
  Purchase #2 $96.92   13.108%   $109.6243   $109.62   $109.60   $109.60  
  Purchase #3 $29.95   7.393%   $32.1642   $32.16   $32.15   $32.20  
  Purchase #4 $65.99   6.392%   $70.2081   $70.21   $70.20   $70.20  
  Purchase #5 $63.71   5.116%   $66.9694   $66.97   $66.95   $67.00  
  Purchase #6 $183.83   4.344%   $191.8156   $191.82   $191.80   $191.80  
  Purchase #7 $44.27   4.830%   $46.4082   $46.41   $46.40   $46.40  
  7 purchase totals = $667.17       $711.9319   $711.93   $711.85   $711.90