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 $102.59   11.109%   $113.9867   $113.99   $114.00   $114.00  
  Purchase #2 $221.97   6.358%   $236.0829   $236.08   $236.10   $236.10  
  Purchase #3 $51.49   4.861%   $53.9929   $53.99   $54.00   $54.00  
  Purchase #4 $166.88   11.240%   $185.6373   $185.64   $185.65   $185.60  
  Purchase #5 $7.96   8.569%   $8.6421   $8.64   $8.65   $8.60  
  Purchase #6 $243.73   10.211%   $268.6173   $268.62   $268.60   $268.60  
  Purchase #7 $55.75   9.536%   $61.0663   $61.07   $61.05   $61.10  
  7 purchase totals = $850.37       $928.0255   $928.03   $928.05   $928.00