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 $196.52   9.831%   $215.8399   $215.84   $215.85   $215.80  
  Purchase #2 $90.87   4.511%   $94.9691   $94.97   $94.95   $95.00  
  Purchase #3 $51.82   12.377%   $58.2338   $58.23   $58.25   $58.20  
  Purchase #4 $46.30   8.308%   $50.1466   $50.15   $50.15   $50.10  
  Purchase #5 $42.28   6.426%   $44.9969   $45.00   $45.00   $45.00  
  Purchase #6 $215.87   9.635%   $236.6691   $236.67   $236.65   $236.70  
  Purchase #7 $243.61   5.866%   $257.9002   $257.90   $257.90   $257.90  
  7 purchase totals = $887.27       $958.7556   $958.76   $958.75   $958.70