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 $208.57   11.227%   $231.9862   $231.99   $232.00   $232.00  
  Purchase #2 $105.70   6.294%   $112.3528   $112.35   $112.35   $112.40  
  Purchase #3 $118.95   12.537%   $133.8628   $133.86   $133.85   $133.90  
  Purchase #4 $48.56   7.295%   $52.1025   $52.10   $52.10   $52.10  
  Purchase #5 $215.62   9.569%   $236.2527   $236.25   $236.25   $236.30  
  Purchase #6 $71.98   6.763%   $76.848   $76.85   $76.85   $76.80  
  Purchase #7 $249.67   13.154%   $282.5116   $282.51   $282.50   $282.50  
  7 purchase totals = $1,019.05       $1,125.9166   $1,125.91   $1,125.90   $1,126.00