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 $32.56   7.454%   $34.987   $34.99   $35.00   $35.00  
  Purchase #2 $132.77   9.637%   $145.565   $145.57   $145.55   $145.60  
  Purchase #3 $7.99   3.389%   $8.2608   $8.26   $8.25   $8.30  
  Purchase #4 $157.95   9.484%   $172.93   $172.93   $172.95   $172.90  
  Purchase #5 $116.37   7.763%   $125.4038   $125.40   $125.40   $125.40  
  Purchase #6 $42.33   4.680%   $44.311   $44.31   $44.30   $44.30  
  Purchase #7 $194.27   5.280%   $204.5275   $204.53   $204.55   $204.50  
  7 purchase totals = $684.24       $735.9851   $735.99   $736.00   $736.00