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 $196.39   5.733%   $207.649   $207.65   $207.65   $207.60  
  Purchase #2 $129.96   10.327%   $143.381   $143.38   $143.40   $143.40  
  Purchase #3 $166.51   9.525%   $182.3701   $182.37   $182.35   $182.40  
  Purchase #4 $120.47   8.380%   $130.5654   $130.57   $130.55   $130.60  
  Purchase #5 $249.92   6.869%   $267.087   $267.09   $267.10   $267.10  
  Purchase #6 $246.39   9.164%   $268.9692   $268.97   $268.95   $269.00  
  Purchase #7 $112.66   11.481%   $125.5945   $125.59   $125.60   $125.60  
  7 purchase totals = $1,222.30       $1,325.6162   $1,325.62   $1,325.60   $1,325.70