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 $212.51   5.862%   $224.9673   $224.97   $224.95   $225.00  
  Purchase #2 $246.93   6.319%   $262.5335   $262.53   $262.55   $262.50  
  Purchase #3 $219.51   12.321%   $246.5558   $246.56   $246.55   $246.60  
  Purchase #4 $194.45   7.476%   $208.9871   $208.99   $209.00   $209.00  
  Purchase #5 $134.26   6.676%   $143.2232   $143.22   $143.20   $143.20  
  Purchase #6 $73.80   3.277%   $76.2184   $76.22   $76.20   $76.20  
  Purchase #7 $249.51   5.185%   $262.4471   $262.45   $262.45   $262.40  
  7 purchase totals = $1,330.97       $1,424.9324   $1,424.94   $1,424.90   $1,424.90