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 $212.75   9.430%   $232.8123   $232.81   $232.80   $232.80  
  Purchase #2 $158.28   10.570%   $175.0102   $175.01   $175.00   $175.00  
  Purchase #3 $119.59   4.798%   $125.3279   $125.33   $125.35   $125.30  
  Purchase #4 $240.90   5.743%   $254.7349   $254.73   $254.75   $254.70  
  Purchase #5 $137.44   12.850%   $155.101   $155.10   $155.10   $155.10  
  Purchase #6 $242.95   6.851%   $259.5945   $259.59   $259.60   $259.60  
  Purchase #7 $245.92   7.447%   $264.2337   $264.23   $264.25   $264.20  
  7 purchase totals = $1,357.83       $1,466.8145   $1,466.80   $1,466.85   $1,466.70