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 $66.76   12.196%   $74.902   $74.90   $74.90   $74.90  
  Purchase #2 $248.46   7.544%   $267.2038   $267.20   $267.20   $267.20  
  Purchase #3 $68.64   5.249%   $72.2429   $72.24   $72.25   $72.20  
  Purchase #4 $93.57   9.813%   $102.752   $102.75   $102.75   $102.80  
  Purchase #5 $177.41   7.429%   $190.5898   $190.59   $190.60   $190.60  
  Purchase #6 $233.50   9.246%   $255.0894   $255.09   $255.10   $255.10  
  Purchase #7 $131.61   10.334%   $145.2106   $145.21   $145.20   $145.20  
  7 purchase totals = $1,019.95       $1,107.9905   $1,107.98   $1,108.00   $1,108.00