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 $205.83   8.788%   $223.9183   $223.92   $223.90   $223.90  
  Purchase #2 $215.85   5.121%   $226.9037   $226.90   $226.90   $226.90  
  Purchase #3 $91.67   6.656%   $97.7716   $97.77   $97.75   $97.80  
  Purchase #4 $215.60   4.240%   $224.7414   $224.74   $224.75   $224.70  
  Purchase #5 $151.90   6.445%   $161.69   $161.69   $161.70   $161.70  
  Purchase #6 $214.49   6.531%   $228.4983   $228.50   $228.50   $228.50  
  Purchase #7 $27.61   5.376%   $29.0943   $29.09   $29.10   $29.10  
  7 purchase totals = $1,122.95       $1,192.6176   $1,192.61   $1,192.60   $1,192.60