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 $243.35   7.843%   $262.4359   $262.44   $262.45   $262.40  
  Purchase #2 $110.54   12.687%   $124.5642   $124.56   $124.55   $124.60  
  Purchase #3 $103.63   10.166%   $114.165   $114.17   $114.15   $114.20  
  Purchase #4 $79.39   10.871%   $88.0205   $88.02   $88.00   $88.00  
  Purchase #5 $195.35   4.473%   $204.088   $204.09   $204.10   $204.10  
  Purchase #6 $170.39   13.698%   $193.73   $193.73   $193.75   $193.70  
  Purchase #7 $157.39   13.159%   $178.101   $178.10   $178.10   $178.10  
  7 purchase totals = $1,060.04       $1,165.1046   $1,165.11   $1,165.10   $1,165.10