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 $192.67   4.736%   $201.7949   $201.79   $201.80   $201.80  
  Purchase #2 $70.85   3.348%   $73.2221   $73.22   $73.20   $73.20  
  Purchase #3 $123.32   9.183%   $134.6445   $134.64   $134.65   $134.60  
  Purchase #4 $105.78   6.866%   $113.0429   $113.04   $113.05   $113.00  
  Purchase #5 $250.49   6.303%   $266.2784   $266.28   $266.30   $266.30  
  Purchase #6 $92.68   5.788%   $98.0443   $98.04   $98.05   $98.00  
  Purchase #7 $122.29   12.561%   $137.6508   $137.65   $137.65   $137.70  
  7 purchase totals = $958.08       $1,024.6779   $1,024.66   $1,024.70   $1,024.60