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 $207.86   11.733%   $232.2482   $232.25   $232.25   $232.20  
  Purchase #2 $165.55   6.827%   $176.8521   $176.85   $176.85   $176.90  
  Purchase #3 $169.31   4.579%   $177.0627   $177.06   $177.05   $177.10  
  Purchase #4 $122.40   7.730%   $131.8615   $131.86   $131.85   $131.90  
  Purchase #5 $205.54   9.605%   $225.2821   $225.28   $225.30   $225.30  
  Purchase #6 $54.35   10.274%   $59.9339   $59.93   $59.95   $59.90  
  Purchase #7 $99.29   13.603%   $112.7964   $112.80   $112.80   $112.80  
  7 purchase totals = $1,024.30       $1,116.0369   $1,116.03   $1,116.05   $1,116.10