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 $248.46   5.474%   $262.0607   $262.06   $262.05   $262.10  
  Purchase #2 $120.82   10.228%   $133.1775   $133.18   $133.20   $133.20  
  Purchase #3 $192.53   7.456%   $206.885   $206.89   $206.90   $206.90  
  Purchase #4 $231.84   6.224%   $246.2697   $246.27   $246.25   $246.30  
  Purchase #5 $122.47   11.262%   $136.2626   $136.26   $136.25   $136.30  
  Purchase #6 $25.94   3.198%   $26.7696   $26.77   $26.75   $26.80  
  Purchase #7 $141.56   11.820%   $158.2924   $158.29   $158.30   $158.30  
  7 purchase totals = $1,083.62       $1,169.7175   $1,169.72   $1,169.70   $1,169.90