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 $211.86   13.862%   $241.228   $241.23   $241.25   $241.20  
  Purchase #2 $159.95   4.140%   $166.5719   $166.57   $166.55   $166.60  
  Purchase #3 $124.59   6.568%   $132.7731   $132.77   $132.75   $132.80  
  Purchase #4 $11.94   13.416%   $13.5419   $13.54   $13.55   $13.50  
  Purchase #5 $127.68   9.588%   $139.922   $139.92   $139.90   $139.90  
  Purchase #6 $202.41   5.844%   $214.2388   $214.24   $214.25   $214.20  
  Purchase #7 $174.82   10.341%   $192.8981   $192.90   $192.90   $192.90  
  7 purchase totals = $1,013.25       $1,101.1738   $1,101.17   $1,101.15   $1,101.10