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 $236.85   10.493%   $261.7027   $261.70   $261.70   $261.70  
  Purchase #2 $249.54   6.198%   $265.0065   $265.01   $265.00   $265.00  
  Purchase #3 $144.64   6.375%   $153.8608   $153.86   $153.85   $153.90  
  Purchase #4 $157.34   10.858%   $174.424   $174.42   $174.40   $174.40  
  Purchase #5 $174.95   5.793%   $185.0849   $185.08   $185.10   $185.10  
  Purchase #6 $16.32   10.872%   $18.0943   $18.09   $18.10   $18.10  
  Purchase #7 $66.25   12.721%   $74.6777   $74.68   $74.70   $74.70  
  7 purchase totals = $1,045.89       $1,132.8509   $1,132.84   $1,132.85   $1,132.90