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 $214.96   8.719%   $233.7024   $233.70   $233.70   $233.70  
  Purchase #2 $16.46   11.569%   $18.3643   $18.36   $18.35   $18.40  
  Purchase #3 $118.36   10.128%   $130.3475   $130.35   $130.35   $130.30  
  Purchase #4 $145.59   8.191%   $157.5153   $157.52   $157.50   $157.50  
  Purchase #5 $55.59   7.328%   $59.6636   $59.66   $59.65   $59.70  
  Purchase #6 $244.62   11.547%   $272.8663   $272.87   $272.85   $272.90  
  Purchase #7 $9.75   7.307%   $10.4624   $10.46   $10.45   $10.50  
  7 purchase totals = $805.33       $882.9218   $882.92   $882.85   $883.00