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 $23.73   9.623%   $26.0135   $26.01   $26.00   $26.00  
  Purchase #2 $191.40   13.257%   $216.7739   $216.77   $216.75   $216.80  
  Purchase #3 $172.27   9.184%   $188.0913   $188.09   $188.10   $188.10  
  Purchase #4 $158.52   7.819%   $170.9147   $170.91   $170.90   $170.90  
  Purchase #5 $232.77   9.191%   $254.1639   $254.16   $254.15   $254.20  
  Purchase #6 $230.73   8.104%   $249.4284   $249.43   $249.45   $249.40  
  Purchase #7 $56.87   9.596%   $62.3272   $62.33   $62.35   $62.30  
  7 purchase totals = $1,066.29       $1,167.7129   $1,167.70   $1,167.70   $1,167.70