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 $168.80   8.263%   $182.7479   $182.75   $182.75   $182.70  
  Purchase #2 $47.28   3.326%   $48.8525   $48.85   $48.85   $48.90  
  Purchase #3 $167.74   13.509%   $190.4   $190.40   $190.40   $190.40  
  Purchase #4 $171.79   11.555%   $191.6403   $191.64   $191.65   $191.60  
  Purchase #5 $141.48   12.431%   $159.0674   $159.07   $159.05   $159.10  
  Purchase #6 $53.34   10.342%   $58.8564   $58.86   $58.85   $58.90  
  Purchase #7 $196.70   12.698%   $221.677   $221.68   $221.70   $221.70  
  7 purchase totals = $947.13       $1,053.2415   $1,053.25   $1,053.25   $1,053.30