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 $195.83   12.351%   $220.017   $220.02   $220.00   $220.00  
  Purchase #2 $46.66   4.322%   $48.6766   $48.68   $48.70   $48.70  
  Purchase #3 $218.86   12.739%   $246.7406   $246.74   $246.75   $246.70  
  Purchase #4 $212.77   13.116%   $240.6769   $240.68   $240.70   $240.70  
  Purchase #5 $169.58   9.329%   $185.4001   $185.40   $185.40   $185.40  
  Purchase #6 $214.54   9.349%   $234.5973   $234.60   $234.60   $234.60  
  Purchase #7 $17.77   6.194%   $18.8707   $18.87   $18.85   $18.90  
  7 purchase totals = $1,076.01       $1,194.9792   $1,194.99   $1,195.00   $1,195.00