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 $71.63   3.236%   $73.9479   $73.95   $73.95   $73.90  
  Purchase #2 $110.93   3.525%   $114.8403   $114.84   $114.85   $114.80  
  Purchase #3 $199.53   13.859%   $227.1829   $227.18   $227.20   $227.20  
  Purchase #4 $29.48   3.761%   $30.5887   $30.59   $30.60   $30.60  
  Purchase #5 $220.76   6.742%   $235.6436   $235.64   $235.65   $235.60  
  Purchase #6 $122.68   5.654%   $129.6163   $129.62   $129.60   $129.60  
  Purchase #7 $233.82   11.176%   $259.9517   $259.95   $259.95   $260.00  
  7 purchase totals = $988.83       $1,071.7714   $1,071.77   $1,071.80   $1,071.70