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 $191.87   9.291%   $209.6966   $209.70   $209.70   $209.70  
  Purchase #2 $73.59   12.373%   $82.6953   $82.70   $82.70   $82.70  
  Purchase #3 $58.80   12.225%   $65.9883   $65.99   $66.00   $66.00  
  Purchase #4 $91.26   4.728%   $95.5748   $95.57   $95.55   $95.60  
  Purchase #5 $104.86   7.731%   $112.9667   $112.97   $112.95   $113.00  
  Purchase #6 $141.62   8.671%   $153.8999   $153.90   $153.90   $153.90  
  Purchase #7 $203.65   13.646%   $231.4401   $231.44   $231.45   $231.40  
  7 purchase totals = $865.65       $952.2617   $952.27   $952.25   $952.30