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 $221.84   11.331%   $246.9767   $246.98   $247.00   $247.00  
  Purchase #2 $24.69   6.424%   $26.2761   $26.28   $26.30   $26.30  
  Purchase #3 $221.25   9.408%   $242.0652   $242.07   $242.05   $242.10  
  Purchase #4 $68.81   11.746%   $76.8924   $76.89   $76.90   $76.90  
  Purchase #5 $216.55   6.457%   $230.5326   $230.53   $230.55   $230.50  
  Purchase #6 $182.51   5.354%   $192.2816   $192.28   $192.30   $192.30  
  Purchase #7 $117.75   11.223%   $130.9651   $130.97   $130.95   $131.00  
  7 purchase totals = $1,053.40       $1,145.9897   $1,146.00   $1,146.05   $1,146.10