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 $162.76   8.133%   $175.9973   $176.00   $176.00   $176.00  
  Purchase #2 $101.86   5.627%   $107.5917   $107.59   $107.60   $107.60  
  Purchase #3 $209.53   3.229%   $216.2957   $216.30   $216.30   $216.30  
  Purchase #4 $29.57   10.538%   $32.6861   $32.69   $32.70   $32.70  
  Purchase #5 $141.90   11.430%   $158.1192   $158.12   $158.10   $158.10  
  Purchase #6 $61.46   11.780%   $68.7   $68.70   $68.70   $68.70  
  Purchase #7 $38.47   13.670%   $43.7288   $43.73   $43.75   $43.70  
  7 purchase totals = $745.55       $803.1188   $803.13   $803.15   $803.10