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 $119.25   5.330%   $125.606   $125.61   $125.60   $125.60  
  Purchase #2 $182.52   5.217%   $192.0421   $192.04   $192.05   $192.00  
  Purchase #3 $71.43   4.284%   $74.4901   $74.49   $74.50   $74.50  
  Purchase #4 $229.47   8.782%   $249.6221   $249.62   $249.60   $249.60  
  Purchase #5 $161.62   13.218%   $182.9829   $182.98   $183.00   $183.00  
  Purchase #6 $234.87   11.674%   $262.2887   $262.29   $262.30   $262.30  
  Purchase #7 $226.43   6.135%   $240.3215   $240.32   $240.30   $240.30  
  7 purchase totals = $1,225.59       $1,327.3534   $1,327.35   $1,327.35   $1,327.30