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 $184.53   5.375%   $194.4485   $194.45   $194.45   $194.40  
  Purchase #2 $246.69   6.570%   $262.8975   $262.90   $262.90   $262.90  
  Purchase #3 $177.78   9.725%   $195.0691   $195.07   $195.05   $195.10  
  Purchase #4 $182.26   12.258%   $204.6014   $204.60   $204.60   $204.60  
  Purchase #5 $146.58   6.569%   $156.2088   $156.21   $156.20   $156.20  
  Purchase #6 $149.54   9.362%   $163.5399   $163.54   $163.55   $163.50  
  Purchase #7 $31.99   9.726%   $35.1013   $35.10   $35.10   $35.10  
  7 purchase totals = $1,119.37       $1,211.8665   $1,211.87   $1,211.85   $1,211.80