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 $61.46   3.678%   $63.7205   $63.72   $63.70   $63.70  
  Purchase #2 $85.56   13.318%   $96.9549   $96.95   $96.95   $97.00  
  Purchase #3 $120.63   5.387%   $127.1283   $127.13   $127.15   $127.10  
  Purchase #4 $234.54   13.488%   $266.1748   $266.17   $266.15   $266.20  
  Purchase #5 $116.63   9.775%   $128.0306   $128.03   $128.05   $128.00  
  Purchase #6 $236.86   10.106%   $260.7971   $260.80   $260.80   $260.80  
  Purchase #7 $203.74   11.376%   $226.9175   $226.92   $226.90   $226.90  
  7 purchase totals = $1,059.42       $1,169.7237   $1,169.72   $1,169.70   $1,169.70