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 $67.97   10.308%   $74.9763   $74.98   $75.00   $75.00  
  Purchase #2 $220.29   11.277%   $245.1321   $245.13   $245.15   $245.10  
  Purchase #3 $217.65   9.223%   $237.7239   $237.72   $237.70   $237.70  
  Purchase #4 $169.90   5.725%   $179.6268   $179.63   $179.65   $179.60  
  Purchase #5 $70.87   10.282%   $78.1569   $78.16   $78.15   $78.20  
  Purchase #6 $170.36   3.407%   $176.1642   $176.16   $176.15   $176.20  
  Purchase #7 $23.28   6.475%   $24.7874   $24.79   $24.80   $24.80  
  7 purchase totals = $940.32       $1,016.5676   $1,016.57   $1,016.60   $1,016.60