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 $114.48   10.521%   $126.5244   $126.52   $126.50   $126.50  
  Purchase #2 $200.29   12.186%   $224.6973   $224.70   $224.70   $224.70  
  Purchase #3 $184.50   7.220%   $197.8209   $197.82   $197.80   $197.80  
  Purchase #4 $136.26   4.763%   $142.7501   $142.75   $142.75   $142.80  
  Purchase #5 $244.47   13.800%   $278.2069   $278.21   $278.20   $278.20  
  Purchase #6 $138.60   9.474%   $151.731   $151.73   $151.75   $151.70  
  Purchase #7 $223.37   8.459%   $242.2649   $242.26   $242.25   $242.30  
  7 purchase totals = $1,241.97       $1,363.9955   $1,363.99   $1,363.95   $1,364.00