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 $91.82   3.420%   $94.9602   $94.96   $94.95   $95.00  
  Purchase #2 $234.95   11.636%   $262.2888   $262.29   $262.30   $262.30  
  Purchase #3 $187.45   5.207%   $197.2105   $197.21   $197.20   $197.20  
  Purchase #4 $106.78   5.286%   $112.4244   $112.42   $112.40   $112.40  
  Purchase #5 $154.88   11.508%   $172.7036   $172.70   $172.70   $172.70  
  Purchase #6 $59.28   11.608%   $66.1612   $66.16   $66.15   $66.20  
  Purchase #7 $130.42   8.487%   $141.4887   $141.49   $141.50   $141.50  
  7 purchase totals = $965.58       $1,047.2374   $1,047.23   $1,047.20   $1,047.30