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 $194.56   5.649%   $205.5507   $205.55   $205.55   $205.60  
  Purchase #2 $175.39   7.420%   $188.4039   $188.40   $188.40   $188.40  
  Purchase #3 $13.59   9.829%   $14.9258   $14.93   $14.95   $14.90  
  Purchase #4 $239.45   11.752%   $267.5902   $267.59   $267.60   $267.60  
  Purchase #5 $121.38   7.835%   $130.8901   $130.89   $130.90   $130.90  
  Purchase #6 $76.30   4.716%   $79.8983   $79.90   $79.90   $79.90  
  Purchase #7 $134.59   11.379%   $149.905   $149.91   $149.90   $149.90  
  7 purchase totals = $955.26       $1,037.1640   $1,037.17   $1,037.20   $1,037.20