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 $219.36   11.682%   $244.9856   $244.99   $245.00   $245.00  
  Purchase #2 $228.69   13.188%   $258.8496   $258.85   $258.85   $258.80  
  Purchase #3 $24.31   8.595%   $26.3994   $26.40   $26.40   $26.40  
  Purchase #4 $8.28   8.448%   $8.9795   $8.98   $9.00   $9.00  
  Purchase #5 $228.51   5.737%   $241.6196   $241.62   $241.60   $241.60  
  Purchase #6 $208.28   6.449%   $221.712   $221.71   $221.70   $221.70  
  Purchase #7 $82.48   12.448%   $92.7471   $92.75   $92.75   $92.70  
  7 purchase totals = $999.91       $1,095.2928   $1,095.30   $1,095.30   $1,095.20