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 $101.40   13.320%   $114.9065   $114.91   $114.90   $114.90  
  Purchase #2 $44.89   4.109%   $46.7345   $46.73   $46.75   $46.70  
  Purchase #3 $210.72   8.255%   $228.1149   $228.11   $228.10   $228.10  
  Purchase #4 $149.91   10.292%   $165.3387   $165.34   $165.35   $165.30  
  Purchase #5 $232.67   5.701%   $245.9345   $245.93   $245.95   $245.90  
  Purchase #6 $225.50   6.841%   $240.9265   $240.93   $240.95   $240.90  
  Purchase #7 $146.69   9.442%   $160.5405   $160.54   $160.55   $160.50  
  7 purchase totals = $1,111.78       $1,202.4961   $1,202.49   $1,202.55   $1,202.30