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 $67.58   11.874%   $75.6044   $75.60   $75.60   $75.60  
  Purchase #2 $191.90   10.307%   $211.6791   $211.68   $211.70   $211.70  
  Purchase #3 $226.78   10.153%   $249.805   $249.81   $249.80   $249.80  
  Purchase #4 $114.37   7.486%   $122.9317   $122.93   $122.95   $122.90  
  Purchase #5 $194.96   10.176%   $214.7991   $214.80   $214.80   $214.80  
  Purchase #6 $242.68   11.418%   $270.3892   $270.39   $270.40   $270.40  
  Purchase #7 $247.74   7.485%   $266.2833   $266.28   $266.30   $266.30  
  7 purchase totals = $1,286.01       $1,411.4918   $1,411.49   $1,411.55   $1,411.50