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 $23.71   9.685%   $26.0063   $26.01   $26.00   $26.00  
  Purchase #2 $198.67   12.669%   $223.8395   $223.84   $223.85   $223.80  
  Purchase #3 $179.85   9.856%   $197.576   $197.58   $197.60   $197.60  
  Purchase #4 $227.27   5.819%   $240.4948   $240.49   $240.50   $240.50  
  Purchase #5 $5.81   8.219%   $6.2875   $6.29   $6.30   $6.30  
  Purchase #6 $213.90   8.597%   $232.289   $232.29   $232.30   $232.30  
  Purchase #7 $200.43   13.509%   $227.5061   $227.51   $227.50   $227.50  
  7 purchase totals = $1,049.64       $1,153.9992   $1,154.01   $1,154.05   $1,154.00