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 $44.39   5.492%   $46.8279   $46.83   $46.85   $46.80  
  Purchase #2 $173.83   7.103%   $186.1771   $186.18   $186.20   $186.20  
  Purchase #3 $230.62   3.587%   $238.8923   $238.89   $238.90   $238.90  
  Purchase #4 $70.27   7.768%   $75.7286   $75.73   $75.75   $75.70  
  Purchase #5 $141.47   5.851%   $149.7474   $149.75   $149.75   $149.70  
  Purchase #6 $10.70   5.623%   $11.3017   $11.30   $11.30   $11.30  
  Purchase #7 $232.98   3.209%   $240.4563   $240.46   $240.45   $240.50  
  7 purchase totals = $904.26       $949.1313   $949.14   $949.20   $949.10