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 $91.69   3.831%   $95.2026   $95.20   $95.20   $95.20  
  Purchase #2 $147.88   3.392%   $152.8961   $152.90   $152.90   $152.90  
  Purchase #3 $207.26   10.871%   $229.7912   $229.79   $229.80   $229.80  
  Purchase #4 $106.83   7.129%   $114.4459   $114.45   $114.45   $114.40  
  Purchase #5 $101.52   9.293%   $110.9543   $110.95   $110.95   $111.00  
  Purchase #6 $176.42   6.650%   $188.1519   $188.15   $188.15   $188.20  
  Purchase #7 $50.47   8.528%   $54.7741   $54.77   $54.75   $54.80  
  7 purchase totals = $882.07       $946.2161   $946.21   $946.20   $946.30