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 $243.41   9.261%   $265.9522   $265.95   $265.95   $266.00  
  Purchase #2 $126.68   6.767%   $135.2524   $135.25   $135.25   $135.30  
  Purchase #3 $49.97   9.634%   $54.7841   $54.78   $54.80   $54.80  
  Purchase #4 $121.56   3.851%   $126.2413   $126.24   $126.25   $126.20  
  Purchase #5 $167.37   6.334%   $177.9712   $177.97   $177.95   $178.00  
  Purchase #6 $233.94   8.733%   $254.37   $254.37   $254.35   $254.40  
  Purchase #7 $150.73   4.332%   $157.2596   $157.26   $157.25   $157.30  
  7 purchase totals = $1,093.66       $1,171.8308   $1,171.82   $1,171.80   $1,172.00