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 $85.65   10.292%   $94.4651   $94.47   $94.45   $94.50  
  Purchase #2 $248.74   12.466%   $279.7479   $279.75   $279.75   $279.70  
  Purchase #3 $53.74   6.804%   $57.3965   $57.40   $57.40   $57.40  
  Purchase #4 $40.95   6.744%   $43.7117   $43.71   $43.70   $43.70  
  Purchase #5 $191.65   5.105%   $201.4337   $201.43   $201.45   $201.40  
  Purchase #6 $245.28   6.264%   $260.6443   $260.64   $260.65   $260.60  
  Purchase #7 $250.61   10.525%   $276.9867   $276.99   $277.00   $277.00  
  7 purchase totals = $1,116.62       $1,214.3859   $1,214.39   $1,214.40   $1,214.30