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 $96.46   6.386%   $102.6199   $102.62   $102.60   $102.60  
  Purchase #2 $184.29   9.533%   $201.8584   $201.86   $201.85   $201.90  
  Purchase #3 $248.96   12.812%   $280.8568   $280.86   $280.85   $280.90  
  Purchase #4 $205.61   9.180%   $224.485   $224.49   $224.50   $224.50  
  Purchase #5 $101.83   10.481%   $112.5028   $112.50   $112.50   $112.50  
  Purchase #6 $53.70   4.840%   $56.2991   $56.30   $56.30   $56.30  
  Purchase #7 $206.50   5.230%   $217.3   $217.30   $217.30   $217.30  
  7 purchase totals = $1,097.35       $1,195.9220   $1,195.93   $1,195.90   $1,196.00