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 $215.30   8.668%   $233.9622   $233.96   $233.95   $234.00  
  Purchase #2 $232.68   11.720%   $259.9501   $259.95   $259.95   $260.00  
  Purchase #3 $78.81   11.111%   $87.5666   $87.57   $87.55   $87.60  
  Purchase #4 $153.84   13.200%   $174.1469   $174.15   $174.15   $174.10  
  Purchase #5 $224.68   5.806%   $237.7249   $237.72   $237.70   $237.70  
  Purchase #6 $167.49   13.716%   $190.4629   $190.46   $190.45   $190.50  
  Purchase #7 $108.53   3.188%   $111.9899   $111.99   $112.00   $112.00  
  7 purchase totals = $1,181.33       $1,295.8035   $1,295.80   $1,295.75   $1,295.90