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 $60.88   3.398%   $62.9487   $62.95   $62.95   $62.90  
  Purchase #2 $193.76   4.378%   $202.2428   $202.24   $202.25   $202.20  
  Purchase #3 $126.44   3.728%   $131.1537   $131.15   $131.15   $131.20  
  Purchase #4 $109.38   8.103%   $118.2431   $118.24   $118.25   $118.20  
  Purchase #5 $60.34   3.727%   $62.5889   $62.59   $62.60   $62.60  
  Purchase #6 $66.80   9.824%   $73.3624   $73.36   $73.35   $73.40  
  Purchase #7 $174.74   5.605%   $184.5342   $184.53   $184.55   $184.50  
  7 purchase totals = $792.34       $835.0738   $835.06   $835.10   $835.00