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 $194.68   5.160%   $204.7255   $204.73   $204.75   $204.70  
  Purchase #2 $155.73   4.219%   $162.3002   $162.30   $162.30   $162.30  
  Purchase #3 $128.54   10.136%   $141.5688   $141.57   $141.55   $141.60  
  Purchase #4 $98.48   5.473%   $103.8698   $103.87   $103.85   $103.90  
  Purchase #5 $214.45   3.390%   $221.7199   $221.72   $221.70   $221.70  
  Purchase #6 $192.45   6.710%   $205.3634   $205.36   $205.35   $205.40  
  Purchase #7 $162.89   8.268%   $176.3577   $176.36   $176.35   $176.40  
  7 purchase totals = $1,147.22       $1,215.9053   $1,215.91   $1,215.85   $1,216.00