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 $91.25   4.592%   $95.4402   $95.44   $95.45   $95.40  
  Purchase #2 $181.49   13.543%   $206.0692   $206.07   $206.05   $206.10  
  Purchase #3 $62.48   7.709%   $67.2966   $67.30   $67.30   $67.30  
  Purchase #4 $112.75   3.866%   $117.1089   $117.11   $117.10   $117.10  
  Purchase #5 $67.89   13.240%   $76.8786   $76.88   $76.90   $76.90  
  Purchase #6 $55.84   13.555%   $63.4091   $63.41   $63.40   $63.40  
  Purchase #7 $100.49   9.419%   $109.9552   $109.96   $109.95   $110.00  
  7 purchase totals = $672.19       $736.1578   $736.17   $736.15   $736.20