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 $45.67   4.190%   $47.5836   $47.58   $47.60   $47.60  
  Purchase #2 $186.65   8.257%   $202.0617   $202.06   $202.05   $202.10  
  Purchase #3 $125.27   3.505%   $129.6607   $129.66   $129.65   $129.70  
  Purchase #4 $207.86   6.624%   $221.6286   $221.63   $221.65   $221.60  
  Purchase #5 $168.67   10.241%   $185.9435   $185.94   $185.95   $185.90  
  Purchase #6 $229.69   3.782%   $238.3769   $238.38   $238.40   $238.40  
  Purchase #7 $191.28   8.626%   $207.7798   $207.78   $207.80   $207.80  
  7 purchase totals = $1,155.09       $1,233.0348   $1,233.03   $1,233.10   $1,233.10