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 $94.43   11.788%   $105.5614   $105.56   $105.55   $105.60  
  Purchase #2 $160.53   10.654%   $177.6329   $177.63   $177.65   $177.60  
  Purchase #3 $8.55   7.858%   $9.2219   $9.22   $9.20   $9.20  
  Purchase #4 $114.96   8.628%   $124.8787   $124.88   $124.90   $124.90  
  Purchase #5 $191.45   4.300%   $199.6824   $199.68   $199.70   $199.70  
  Purchase #6 $64.76   5.159%   $68.101   $68.10   $68.10   $68.10  
  Purchase #7 $91.54   5.253%   $96.3486   $96.35   $96.35   $96.30  
  7 purchase totals = $726.22       $781.4269   $781.42   $781.45   $781.40