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 $215.71   8.343%   $233.7067   $233.71   $233.70   $233.70  
  Purchase #2 $172.85   9.247%   $188.8334   $188.83   $188.85   $188.80  
  Purchase #3 $141.90   12.708%   $159.9327   $159.93   $159.95   $159.90  
  Purchase #4 $238.83   13.491%   $271.0506   $271.05   $271.05   $271.10  
  Purchase #5 $222.51   12.584%   $250.5107   $250.51   $250.50   $250.50  
  Purchase #6 $115.92   11.231%   $128.939   $128.94   $128.95   $128.90  
  Purchase #7 $212.91   8.129%   $230.2175   $230.22   $230.20   $230.20  
  7 purchase totals = $1,320.63       $1,463.1906   $1,463.19   $1,463.20   $1,463.10