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 $212.26   13.608%   $241.1443   $241.14   $241.15   $241.10  
  Purchase #2 $74.53   4.118%   $77.5991   $77.60   $77.60   $77.60  
  Purchase #3 $225.76   7.412%   $242.4933   $242.49   $242.50   $242.50  
  Purchase #4 $70.69   6.235%   $75.0975   $75.10   $75.10   $75.10  
  Purchase #5 $88.42   8.695%   $96.1081   $96.11   $96.10   $96.10  
  Purchase #6 $224.52   4.756%   $235.1982   $235.20   $235.20   $235.20  
  Purchase #7 $227.88   12.337%   $255.9936   $255.99   $256.00   $256.00  
  7 purchase totals = $1,124.06       $1,223.6341   $1,223.63   $1,223.65   $1,223.60