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 $114.66   9.432%   $125.4747   $125.47   $125.45   $125.50  
  Purchase #2 $182.54   13.552%   $207.2778   $207.28   $207.30   $207.30  
  Purchase #3 $88.62   9.521%   $97.0575   $97.06   $97.05   $97.10  
  Purchase #4 $90.47   7.614%   $97.3584   $97.36   $97.35   $97.40  
  Purchase #5 $22.45   8.779%   $24.4209   $24.42   $24.40   $24.40  
  Purchase #6 $150.59   4.252%   $156.9931   $156.99   $157.00   $157.00  
  Purchase #7 $148.57   3.454%   $153.7016   $153.70   $153.70   $153.70  
  7 purchase totals = $797.90       $862.2840   $862.28   $862.25   $862.40