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 $207.45   9.714%   $227.6017   $227.60   $227.60   $227.60  
  Purchase #2 $51.68   12.366%   $58.0707   $58.07   $58.05   $58.10  
  Purchase #3 $221.35   4.320%   $230.9123   $230.91   $230.90   $230.90  
  Purchase #4 $217.57   11.298%   $242.1511   $242.15   $242.15   $242.20  
  Purchase #5 $173.36   7.744%   $186.785   $186.79   $186.80   $186.80  
  Purchase #6 $82.42   12.851%   $93.0118   $93.01   $93.00   $93.00  
  Purchase #7 $67.63   6.390%   $71.9516   $71.95   $71.95   $72.00  
  7 purchase totals = $1,021.46       $1,110.4842   $1,110.48   $1,110.45   $1,110.60