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 $185.41   10.771%   $205.3805   $205.38   $205.40   $205.40  
  Purchase #2 $67.41   13.604%   $76.5805   $76.58   $76.60   $76.60  
  Purchase #3 $41.87   10.116%   $46.1056   $46.11   $46.10   $46.10  
  Purchase #4 $87.29   6.315%   $92.8024   $92.80   $92.80   $92.80  
  Purchase #5 $220.88   10.589%   $244.269   $244.27   $244.25   $244.30  
  Purchase #6 $90.30   6.389%   $96.0693   $96.07   $96.05   $96.10  
  Purchase #7 $30.98   11.727%   $34.613   $34.61   $34.60   $34.60  
  7 purchase totals = $724.14       $795.8203   $795.82   $795.80   $795.90