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 $196.93   6.102%   $208.9467   $208.95   $208.95   $208.90  
  Purchase #2 $193.41   13.207%   $218.9537   $218.95   $218.95   $219.00  
  Purchase #3 $218.87   10.572%   $242.0089   $242.01   $242.00   $242.00  
  Purchase #4 $210.63   5.183%   $221.547   $221.55   $221.55   $221.50  
  Purchase #5 $169.26   8.277%   $183.2697   $183.27   $183.25   $183.30  
  Purchase #6 $206.65   11.728%   $230.8859   $230.89   $230.90   $230.90  
  Purchase #7 $128.50   6.216%   $136.4876   $136.49   $136.50   $136.50  
  7 purchase totals = $1,324.25       $1,442.0995   $1,442.11   $1,442.10   $1,442.10