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 $116.83   7.453%   $125.5373   $125.54   $125.55   $125.50  
  Purchase #2 $244.64   12.479%   $275.1686   $275.17   $275.15   $275.20  
  Purchase #3 $193.28   5.821%   $204.5308   $204.53   $204.55   $204.50  
  Purchase #4 $157.66   3.552%   $163.2601   $163.26   $163.25   $163.30  
  Purchase #5 $26.66   10.195%   $29.378   $29.38   $29.40   $29.40  
  Purchase #6 $193.53   4.151%   $201.5634   $201.56   $201.55   $201.60  
  Purchase #7 $86.34   9.409%   $94.4637   $94.46   $94.45   $94.50  
  7 purchase totals = $1,018.94       $1,093.9019   $1,093.90   $1,093.90   $1,094.00