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 $117.70   7.602%   $126.6476   $126.65   $126.65   $126.60  
  Purchase #2 $189.58   13.477%   $215.1297   $215.13   $215.15   $215.10  
  Purchase #3 $118.85   11.703%   $132.759   $132.76   $132.75   $132.80  
  Purchase #4 $178.94   10.612%   $197.9291   $197.93   $197.95   $197.90  
  Purchase #5 $153.43   4.717%   $160.6673   $160.67   $160.65   $160.70  
  Purchase #6 $67.68   6.792%   $72.2768   $72.28   $72.30   $72.30  
  Purchase #7 $165.87   8.771%   $180.4185   $180.42   $180.40   $180.40  
  7 purchase totals = $992.05       $1,085.8280   $1,085.84   $1,085.85   $1,085.80