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 $59.43   4.275%   $61.9706   $61.97   $61.95   $62.00  
  Purchase #2 $79.61   3.173%   $82.136   $82.14   $82.15   $82.10  
  Purchase #3 $9.45   11.697%   $10.5554   $10.56   $10.55   $10.60  
  Purchase #4 $209.61   12.850%   $236.5449   $236.54   $236.55   $236.50  
  Purchase #5 $169.27   11.241%   $188.2976   $188.30   $188.30   $188.30  
  Purchase #6 $217.33   4.274%   $226.6187   $226.62   $226.60   $226.60  
  Purchase #7 $23.55   8.649%   $25.5868   $25.59   $25.60   $25.60  
  7 purchase totals = $768.25       $831.7100   $831.72   $831.70   $831.70