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 $101.75   12.593%   $114.5634   $114.56   $114.55   $114.60  
  Purchase #2 $207.67   12.592%   $233.8198   $233.82   $233.80   $233.80  
  Purchase #3 $211.94   13.221%   $239.9606   $239.96   $239.95   $240.00  
  Purchase #4 $210.35   10.359%   $232.1402   $232.14   $232.15   $232.10  
  Purchase #5 $65.26   3.778%   $67.7255   $67.73   $67.75   $67.70  
  Purchase #6 $203.99   4.555%   $213.2817   $213.28   $213.30   $213.30  
  Purchase #7 $67.83   12.140%   $76.0646   $76.06   $76.05   $76.10  
  7 purchase totals = $1,068.79       $1,177.5558   $1,177.55   $1,177.55   $1,177.60