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 $207.49   3.136%   $213.9969   $214.00   $214.00   $214.00  
  Purchase #2 $89.52   6.165%   $95.0389   $95.04   $95.05   $95.00  
  Purchase #3 $159.53   5.732%   $168.6743   $168.67   $168.65   $168.70  
  Purchase #4 $166.96   13.665%   $189.7751   $189.78   $189.80   $189.80  
  Purchase #5 $115.90   8.387%   $125.6205   $125.62   $125.60   $125.60  
  Purchase #6 $120.41   3.393%   $124.4955   $124.50   $124.50   $124.50  
  Purchase #7 $183.72   12.356%   $206.4204   $206.42   $206.40   $206.40  
  7 purchase totals = $1,043.53       $1,124.0216   $1,124.03   $1,124.00   $1,124.00