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 $232.76   9.811%   $255.5961   $255.60   $255.60   $255.60  
  Purchase #2 $112.50   12.632%   $126.711   $126.71   $126.70   $126.70  
  Purchase #3 $178.30   4.389%   $186.1256   $186.13   $186.15   $186.10  
  Purchase #4 $15.92   10.352%   $17.568   $17.57   $17.55   $17.60  
  Purchase #5 $208.26   13.721%   $236.8354   $236.84   $236.85   $236.80  
  Purchase #6 $200.56   8.140%   $216.8856   $216.89   $216.90   $216.90  
  Purchase #7 $13.52   10.239%   $14.9043   $14.90   $14.90   $14.90  
  7 purchase totals = $961.82       $1,054.6260   $1,054.64   $1,054.65   $1,054.60