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 $181.36   10.865%   $201.0648   $201.06   $201.05   $201.10  
  Purchase #2 $237.68   3.607%   $246.2531   $246.25   $246.25   $246.30  
  Purchase #3 $75.73   4.188%   $78.9016   $78.90   $78.90   $78.90  
  Purchase #4 $225.66   9.665%   $247.47   $247.47   $247.45   $247.50  
  Purchase #5 $220.78   6.174%   $234.411   $234.41   $234.40   $234.40  
  Purchase #6 $154.40   8.704%   $167.839   $167.84   $167.85   $167.80  
  Purchase #7 $170.40   7.600%   $183.3504   $183.35   $183.35   $183.40  
  7 purchase totals = $1,266.01       $1,359.2899   $1,359.28   $1,359.25   $1,359.40