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 $68.43   8.727%   $74.4019   $74.40   $74.40   $74.40  
  Purchase #2 $123.61   10.194%   $136.2108   $136.21   $136.20   $136.20  
  Purchase #3 $115.62   5.241%   $121.6796   $121.68   $121.70   $121.70  
  Purchase #4 $214.30   7.185%   $229.6975   $229.70   $229.70   $229.70  
  Purchase #5 $242.41   13.298%   $274.6457   $274.65   $274.65   $274.60  
  Purchase #6 $62.95   12.159%   $70.6041   $70.60   $70.60   $70.60  
  Purchase #7 $234.31   4.465%   $244.7719   $244.77   $244.75   $244.80  
  7 purchase totals = $1,061.63       $1,152.0115   $1,152.01   $1,152.00   $1,152.00