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 $68.95   10.608%   $76.2642   $76.26   $76.25   $76.30  
  Purchase #2 $33.47   7.249%   $35.8962   $35.90   $35.90   $35.90  
  Purchase #3 $72.48   6.874%   $77.4623   $77.46   $77.45   $77.50  
  Purchase #4 $240.78   13.304%   $272.8134   $272.81   $272.80   $272.80  
  Purchase #5 $114.63   4.131%   $119.3654   $119.37   $119.35   $119.40  
  Purchase #6 $13.65   3.164%   $14.0819   $14.08   $14.10   $14.10  
  Purchase #7 $92.39   7.720%   $99.5225   $99.52   $99.50   $99.50  
  7 purchase totals = $636.35       $695.4059   $695.40   $695.35   $695.50