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 $214.39   6.748%   $228.857   $228.86   $228.85   $228.90  
  Purchase #2 $70.25   3.245%   $72.5296   $72.53   $72.55   $72.50  
  Purchase #3 $200.33   3.611%   $207.5639   $207.56   $207.55   $207.60  
  Purchase #4 $114.70   13.610%   $130.3107   $130.31   $130.30   $130.30  
  Purchase #5 $159.71   9.295%   $174.555   $174.56   $174.55   $174.60  
  Purchase #6 $248.82   8.311%   $269.4994   $269.50   $269.50   $269.50  
  Purchase #7 $173.35   6.299%   $184.2693   $184.27   $184.25   $184.30  
  7 purchase totals = $1,181.55       $1,267.5849   $1,267.59   $1,267.55   $1,267.70