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 $88.46   8.581%   $96.0508   $96.05   $96.05   $96.10  
  Purchase #2 $246.81   10.321%   $272.2833   $272.28   $272.30   $272.30  
  Purchase #3 $211.88   4.358%   $221.1137   $221.11   $221.10   $221.10  
  Purchase #4 $178.92   3.447%   $185.0874   $185.09   $185.10   $185.10  
  Purchase #5 $149.51   5.503%   $157.7375   $157.74   $157.75   $157.70  
  Purchase #6 $16.86   4.594%   $17.6345   $17.63   $17.65   $17.60  
  Purchase #7 $70.75   5.316%   $74.5111   $74.51   $74.50   $74.50  
  7 purchase totals = $963.19       $1,024.4183   $1,024.41   $1,024.45   $1,024.40