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 $208.81   13.319%   $236.6214   $236.62   $236.60   $236.60  
  Purchase #2 $76.60   4.421%   $79.9865   $79.99   $80.00   $80.00  
  Purchase #3 $143.46   10.420%   $158.4085   $158.41   $158.40   $158.40  
  Purchase #4 $249.71   10.158%   $275.0755   $275.08   $275.10   $275.10  
  Purchase #5 $125.33   12.745%   $141.3033   $141.30   $141.30   $141.30  
  Purchase #6 $112.99   3.657%   $117.122   $117.12   $117.10   $117.10  
  Purchase #7 $146.96   10.805%   $162.839   $162.84   $162.85   $162.80  
  7 purchase totals = $1,063.86       $1,171.3562   $1,171.36   $1,171.35   $1,171.30