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 $207.60   3.413%   $214.6854   $214.69   $214.70   $214.70  
  Purchase #2 $147.50   8.327%   $159.7823   $159.78   $159.80   $159.80  
  Purchase #3 $103.26   9.267%   $112.8291   $112.83   $112.85   $112.80  
  Purchase #4 $16.68   10.412%   $18.4167   $18.42   $18.40   $18.40  
  Purchase #5 $84.90   7.409%   $91.1902   $91.19   $91.20   $91.20  
  Purchase #6 $101.27   5.615%   $106.9563   $106.96   $106.95   $107.00  
  Purchase #7 $86.72   6.188%   $92.0862   $92.09   $92.10   $92.10  
  7 purchase totals = $747.93       $795.9462   $795.96   $796.00   $796.00