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 $94.86   10.417%   $104.7416   $104.74   $104.75   $104.70  
  Purchase #2 $194.77   9.527%   $213.3257   $213.33   $213.35   $213.30  
  Purchase #3 $43.91   7.178%   $47.0619   $47.06   $47.05   $47.10  
  Purchase #4 $250.77   4.412%   $261.834   $261.83   $261.85   $261.80  
  Purchase #5 $187.81   10.109%   $206.7957   $206.80   $206.80   $206.80  
  Purchase #6 $118.86   13.704%   $135.1486   $135.15   $135.15   $135.10  
  Purchase #7 $244.81   9.251%   $267.4574   $267.46   $267.45   $267.50  
  7 purchase totals = $1,135.79       $1,236.3649   $1,236.37   $1,236.40   $1,236.30