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 $241.69   7.657%   $260.1962   $260.20   $260.20   $260.20  
  Purchase #2 $163.25   11.142%   $181.4393   $181.44   $181.45   $181.40  
  Purchase #3 $201.40   12.458%   $226.4904   $226.49   $226.50   $226.50  
  Purchase #4 $61.73   11.825%   $69.0296   $69.03   $69.05   $69.00  
  Purchase #5 $108.75   5.465%   $114.6932   $114.69   $114.70   $114.70  
  Purchase #6 $196.31   6.575%   $209.2174   $209.22   $209.20   $209.20  
  Purchase #7 $98.82   11.195%   $109.8829   $109.88   $109.90   $109.90  
  7 purchase totals = $1,071.95       $1,170.9490   $1,170.95   $1,171.00   $1,170.90