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 $207.86   13.782%   $236.5073   $236.51   $236.50   $236.50  
  Purchase #2 $34.50   8.566%   $37.4553   $37.46   $37.45   $37.50  
  Purchase #3 $246.64   11.376%   $274.6978   $274.70   $274.70   $274.70  
  Purchase #4 $22.83   3.184%   $23.5569   $23.56   $23.55   $23.60  
  Purchase #5 $209.77   12.578%   $236.1549   $236.15   $236.15   $236.20  
  Purchase #6 $245.52   10.595%   $271.5328   $271.53   $271.55   $271.50  
  Purchase #7 $104.55   11.701%   $116.7834   $116.78   $116.80   $116.80  
  7 purchase totals = $1,071.67       $1,196.6884   $1,196.69   $1,196.70   $1,196.80