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 $71.64   4.340%   $74.7492   $74.75   $74.75   $74.70  
  Purchase #2 $144.95   4.659%   $151.7032   $151.70   $151.70   $151.70  
  Purchase #3 $80.41   11.597%   $89.7351   $89.74   $89.75   $89.70  
  Purchase #4 $152.42   5.393%   $160.64   $160.64   $160.65   $160.60  
  Purchase #5 $199.46   7.704%   $214.8264   $214.83   $214.85   $214.80  
  Purchase #6 $110.31   12.690%   $124.3083   $124.31   $124.30   $124.30  
  Purchase #7 $198.25   9.207%   $216.5029   $216.50   $216.50   $216.50  
  7 purchase totals = $957.44       $1,032.4651   $1,032.47   $1,032.50   $1,032.30