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 $91.99   3.245%   $94.9751   $94.98   $95.00   $95.00  
  Purchase #2 $13.49   13.504%   $15.3117   $15.31   $15.30   $15.30  
  Purchase #3 $101.85   5.783%   $107.74   $107.74   $107.75   $107.70  
  Purchase #4 $88.75   12.252%   $99.6237   $99.62   $99.60   $99.60  
  Purchase #5 $63.67   5.571%   $67.2171   $67.22   $67.20   $67.20  
  Purchase #6 $248.58   10.335%   $274.2707   $274.27   $274.25   $274.30  
  Purchase #7 $228.97   11.350%   $254.9581   $254.96   $254.95   $255.00  
  7 purchase totals = $837.30       $914.0964   $914.10   $914.05   $914.10