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 $96.86   13.343%   $109.784   $109.78   $109.80   $109.80  
  Purchase #2 $221.71   6.845%   $236.886   $236.89   $236.90   $236.90  
  Purchase #3 $217.42   4.171%   $226.4886   $226.49   $226.50   $226.50  
  Purchase #4 $97.66   11.403%   $108.7962   $108.80   $108.80   $108.80  
  Purchase #5 $171.36   3.568%   $177.4741   $177.47   $177.45   $177.50  
  Purchase #6 $131.88   7.692%   $142.0242   $142.02   $142.00   $142.00  
  Purchase #7 $229.82   13.339%   $260.4757   $260.48   $260.50   $260.50  
  7 purchase totals = $1,166.71       $1,261.9288   $1,261.93   $1,261.95   $1,262.00