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 $182.76   8.428%   $198.163   $198.16   $198.15   $198.20  
  Purchase #2 $123.88   10.563%   $136.9654   $136.97   $136.95   $137.00  
  Purchase #3 $186.43   10.779%   $206.5253   $206.53   $206.55   $206.50  
  Purchase #4 $73.27   4.119%   $76.288   $76.29   $76.30   $76.30  
  Purchase #5 $53.63   7.732%   $57.7767   $57.78   $57.80   $57.80  
  Purchase #6 $227.86   11.266%   $253.5307   $253.53   $253.55   $253.50  
  Purchase #7 $196.97   3.361%   $203.5902   $203.59   $203.60   $203.60  
  7 purchase totals = $1,044.80       $1,132.8393   $1,132.85   $1,132.90   $1,132.90