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 $242.37   11.148%   $269.3894   $269.39   $269.40   $269.40  
  Purchase #2 $111.30   12.307%   $124.9977   $125.00   $125.00   $125.00  
  Purchase #3 $62.56   8.538%   $67.9014   $67.90   $67.90   $67.90  
  Purchase #4 $49.26   9.148%   $53.7663   $53.77   $53.75   $53.80  
  Purchase #5 $211.99   5.345%   $223.3209   $223.32   $223.30   $223.30  
  Purchase #6 $239.83   12.237%   $269.178   $269.18   $269.20   $269.20  
  Purchase #7 $90.40   8.604%   $98.178   $98.18   $98.20   $98.20  
  7 purchase totals = $1,007.71       $1,106.7317   $1,106.74   $1,106.75   $1,106.80