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 $211.84   11.181%   $235.5258   $235.53   $235.55   $235.50  
  Purchase #2 $82.69   10.686%   $91.5263   $91.53   $91.55   $91.50  
  Purchase #3 $96.44   4.496%   $100.7759   $100.78   $100.80   $100.80  
  Purchase #4 $126.54   11.412%   $140.9807   $140.98   $141.00   $141.00  
  Purchase #5 $166.33   5.116%   $174.8394   $174.84   $174.85   $174.80  
  Purchase #6 $166.76   9.556%   $182.6956   $182.70   $182.70   $182.70  
  Purchase #7 $157.83   7.209%   $169.208   $169.21   $169.20   $169.20  
  7 purchase totals = $1,008.43       $1,095.5517   $1,095.57   $1,095.65   $1,095.50