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 $95.28   8.265%   $103.1549   $103.15   $103.15   $103.20  
  Purchase #2 $248.81   7.567%   $267.6375   $267.64   $267.65   $267.60  
  Purchase #3 $189.77   8.519%   $205.9365   $205.94   $205.95   $205.90  
  Purchase #4 $109.50   8.444%   $118.7462   $118.75   $118.75   $118.70  
  Purchase #5 $189.33   7.647%   $203.8081   $203.81   $203.80   $203.80  
  Purchase #6 $239.26   11.263%   $266.2079   $266.21   $266.20   $266.20  
  Purchase #7 $241.96   8.552%   $262.6524   $262.65   $262.65   $262.70  
  7 purchase totals = $1,313.91       $1,428.1435   $1,428.15   $1,428.15   $1,428.10