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 $176.57   3.237%   $182.2856   $182.29   $182.30   $182.30  
  Purchase #2 $145.28   3.784%   $150.7774   $150.78   $150.80   $150.80  
  Purchase #3 $126.63   4.666%   $132.5386   $132.54   $132.55   $132.50  
  Purchase #4 $44.31   4.510%   $46.3084   $46.31   $46.30   $46.30  
  Purchase #5 $49.87   6.670%   $53.1963   $53.20   $53.20   $53.20  
  Purchase #6 $215.34   9.245%   $235.2482   $235.25   $235.25   $235.20  
  Purchase #7 $197.25   6.859%   $210.7794   $210.78   $210.80   $210.80  
  7 purchase totals = $955.25       $1,011.1339   $1,011.15   $1,011.20   $1,011.10