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 $119.62   4.452%   $124.9455   $124.95   $124.95   $124.90  
  Purchase #2 $7.85   3.844%   $8.1518   $8.15   $8.15   $8.20  
  Purchase #3 $219.38   11.143%   $243.8255   $243.83   $243.85   $243.80  
  Purchase #4 $106.59   4.507%   $111.394   $111.39   $111.40   $111.40  
  Purchase #5 $168.48   11.497%   $187.8501   $187.85   $187.85   $187.90  
  Purchase #6 $101.71   12.363%   $114.2844   $114.28   $114.30   $114.30  
  Purchase #7 $233.97   5.781%   $247.4958   $247.50   $247.50   $247.50  
  7 purchase totals = $957.60       $1,037.9471   $1,037.95   $1,038.00   $1,038.00