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 $41.87   4.187%   $43.6231   $43.62   $43.60   $43.60  
  Purchase #2 $201.34   3.557%   $208.5017   $208.50   $208.50   $208.50  
  Purchase #3 $63.26   7.697%   $68.1291   $68.13   $68.15   $68.10  
  Purchase #4 $153.85   9.524%   $168.5027   $168.50   $168.50   $168.50  
  Purchase #5 $40.78   12.872%   $46.0292   $46.03   $46.05   $46.00  
  Purchase #6 $161.33   10.275%   $177.9067   $177.91   $177.90   $177.90  
  Purchase #7 $31.85   6.776%   $34.0082   $34.01   $34.00   $34.00  
  7 purchase totals = $694.28       $746.7007   $746.70   $746.70   $746.60