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 $61.63   3.253%   $63.6348   $63.63   $63.65   $63.60  
  Purchase #2 $118.42   9.548%   $129.7267   $129.73   $129.75   $129.70  
  Purchase #3 $250.26   8.736%   $272.1227   $272.12   $272.10   $272.10  
  Purchase #4 $220.70   11.259%   $245.5486   $245.55   $245.55   $245.50  
  Purchase #5 $248.88   4.152%   $259.2135   $259.21   $259.20   $259.20  
  Purchase #6 $30.77   6.509%   $32.7728   $32.77   $32.75   $32.80  
  Purchase #7 $39.32   12.733%   $44.3266   $44.33   $44.35   $44.30  
  7 purchase totals = $969.98       $1,047.3457   $1,047.34   $1,047.35   $1,047.20