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 $56.45   11.726%   $63.0693   $63.07   $63.05   $63.10  
  Purchase #2 $192.50   8.864%   $209.5632   $209.56   $209.55   $209.60  
  Purchase #3 $153.34   11.618%   $171.155   $171.16   $171.15   $171.20  
  Purchase #4 $151.45   4.483%   $158.2395   $158.24   $158.25   $158.20  
  Purchase #5 $109.75   8.392%   $118.9602   $118.96   $118.95   $119.00  
  Purchase #6 $187.77   12.389%   $211.0328   $211.03   $211.05   $211.00  
  Purchase #7 $96.44   5.386%   $101.6343   $101.63   $101.65   $101.60  
  7 purchase totals = $947.70       $1,033.6543   $1,033.65   $1,033.65   $1,033.70