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 $148.82   10.764%   $164.839   $164.84   $164.85   $164.80  
  Purchase #2 $208.88   11.498%   $232.897   $232.90   $232.90   $232.90  
  Purchase #3 $101.96   4.754%   $106.8072   $106.81   $106.80   $106.80  
  Purchase #4 $115.76   13.220%   $131.0635   $131.06   $131.05   $131.10  
  Purchase #5 $249.45   3.864%   $259.0887   $259.09   $259.10   $259.10  
  Purchase #6 $103.71   13.507%   $117.7181   $117.72   $117.70   $117.70  
  Purchase #7 $174.45   10.416%   $192.6207   $192.62   $192.60   $192.60  
  7 purchase totals = $1,103.03       $1,205.0342   $1,205.04   $1,205.00   $1,205.00