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 $118.76   11.294%   $132.1728   $132.17   $132.15   $132.20  
  Purchase #2 $117.56   13.507%   $133.4388   $133.44   $133.45   $133.40  
  Purchase #3 $244.59   9.677%   $268.259   $268.26   $268.25   $268.30  
  Purchase #4 $165.44   7.130%   $177.2359   $177.24   $177.25   $177.20  
  Purchase #5 $68.38   4.813%   $71.6711   $71.67   $71.65   $71.70  
  Purchase #6 $203.92   12.325%   $229.0531   $229.05   $229.05   $229.10  
  Purchase #7 $10.39   5.181%   $10.9283   $10.93   $10.95   $10.90  
  7 purchase totals = $929.04       $1,022.7590   $1,022.76   $1,022.75   $1,022.80