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 $182.82   7.193%   $195.9702   $195.97   $195.95   $196.00  
  Purchase #2 $60.32   13.604%   $68.5259   $68.53   $68.55   $68.50  
  Purchase #3 $160.36   4.435%   $167.472   $167.47   $167.45   $167.50  
  Purchase #4 $66.49   13.419%   $75.4123   $75.41   $75.40   $75.40  
  Purchase #5 $70.30   8.451%   $76.2411   $76.24   $76.25   $76.20  
  Purchase #6 $161.63   11.306%   $179.9039   $179.90   $179.90   $179.90  
  Purchase #7 $106.83   11.294%   $118.8954   $118.90   $118.90   $118.90  
  7 purchase totals = $808.75       $882.4208   $882.42   $882.40   $882.40