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 $109.74   3.841%   $113.9551   $113.96   $113.95   $114.00  
  Purchase #2 $246.57   13.631%   $280.18   $280.18   $280.20   $280.20  
  Purchase #3 $152.27   9.610%   $166.9031   $166.90   $166.90   $166.90  
  Purchase #4 $241.43   12.457%   $271.5049   $271.50   $271.50   $271.50  
  Purchase #5 $144.54   6.543%   $153.9973   $154.00   $154.00   $154.00  
  Purchase #6 $141.75   6.439%   $150.8773   $150.88   $150.90   $150.90  
  Purchase #7 $215.43   3.508%   $222.9873   $222.99   $223.00   $223.00  
  7 purchase totals = $1,251.73       $1,360.4050   $1,360.41   $1,360.45   $1,360.50