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 $47.26   5.303%   $49.7662   $49.77   $49.75   $49.80  
  Purchase #2 $124.39   4.305%   $129.745   $129.75   $129.75   $129.70  
  Purchase #3 $58.29   13.495%   $66.1562   $66.16   $66.15   $66.20  
  Purchase #4 $246.56   9.302%   $269.495   $269.50   $269.50   $269.50  
  Purchase #5 $169.47   12.261%   $190.2487   $190.25   $190.25   $190.20  
  Purchase #6 $168.73   8.706%   $183.4196   $183.42   $183.40   $183.40  
  Purchase #7 $231.42   9.334%   $253.0207   $253.02   $253.00   $253.00  
  7 purchase totals = $1,046.12       $1,141.8514   $1,141.87   $1,141.80   $1,141.80