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 $84.88   12.326%   $95.3423   $95.34   $95.35   $95.30  
  Purchase #2 $162.51   4.329%   $169.5451   $169.55   $169.55   $169.50  
  Purchase #3 $228.26   8.797%   $248.34   $248.34   $248.35   $248.30  
  Purchase #4 $173.68   8.275%   $188.052   $188.05   $188.05   $188.10  
  Purchase #5 $45.74   11.379%   $50.9448   $50.94   $50.95   $50.90  
  Purchase #6 $241.38   3.364%   $249.5   $249.50   $249.50   $249.50  
  Purchase #7 $96.96   7.669%   $104.3959   $104.40   $104.40   $104.40  
  7 purchase totals = $1,033.41       $1,106.1201   $1,106.12   $1,106.15   $1,106.00