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 $161.91   6.868%   $173.03   $173.03   $173.05   $173.00  
  Purchase #2 $131.27   6.671%   $140.027   $140.03   $140.05   $140.00  
  Purchase #3 $211.41   10.397%   $233.3903   $233.39   $233.40   $233.40  
  Purchase #4 $245.77   6.618%   $262.0351   $262.04   $262.05   $262.00  
  Purchase #5 $62.49   4.313%   $65.1852   $65.19   $65.20   $65.20  
  Purchase #6 $68.83   11.372%   $76.6573   $76.66   $76.65   $76.70  
  Purchase #7 $54.93   6.384%   $58.4367   $58.44   $58.45   $58.40  
  7 purchase totals = $936.61       $1,008.7616   $1,008.78   $1,008.85   $1,008.70