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 $88.97   8.509%   $96.5405   $96.54   $96.55   $96.50  
  Purchase #2 $152.59   3.607%   $158.0939   $158.09   $158.10   $158.10  
  Purchase #3 $124.39   13.522%   $141.21   $141.21   $141.20   $141.20  
  Purchase #4 $187.55   11.560%   $209.2308   $209.23   $209.25   $209.20  
  Purchase #5 $114.45   10.660%   $126.6504   $126.65   $126.65   $126.70  
  Purchase #6 $141.64   4.787%   $148.4203   $148.42   $148.40   $148.40  
  Purchase #7 $148.88   13.594%   $169.1187   $169.12   $169.10   $169.10  
  7 purchase totals = $958.47       $1,049.2646   $1,049.26   $1,049.25   $1,049.20