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 $196.74   5.690%   $207.9345   $207.93   $207.95   $207.90  
  Purchase #2 $105.46   11.775%   $117.8779   $117.88   $117.90   $117.90  
  Purchase #3 $148.87   6.249%   $158.1729   $158.17   $158.15   $158.20  
  Purchase #4 $204.73   4.802%   $214.5611   $214.56   $214.55   $214.60  
  Purchase #5 $15.50   13.602%   $17.6083   $17.61   $17.60   $17.60  
  Purchase #6 $176.77   6.425%   $188.1275   $188.13   $188.15   $188.10  
  Purchase #7 $138.94   5.116%   $146.0482   $146.05   $146.05   $146.00  
  7 purchase totals = $987.01       $1,050.3304   $1,050.33   $1,050.35   $1,050.30