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 $236.41   3.610%   $244.9444   $244.94   $244.95   $244.90  
  Purchase #2 $35.42   3.862%   $36.7879   $36.79   $36.80   $36.80  
  Purchase #3 $36.42   3.133%   $37.561   $37.56   $37.55   $37.60  
  Purchase #4 $23.47   11.630%   $26.1996   $26.20   $26.20   $26.20  
  Purchase #5 $228.36   9.789%   $250.7142   $250.71   $250.70   $250.70  
  Purchase #6 $183.58   3.586%   $190.1632   $190.16   $190.15   $190.20  
  Purchase #7 $217.71   9.775%   $238.9912   $238.99   $239.00   $239.00  
  7 purchase totals = $961.37       $1,025.3615   $1,025.35   $1,025.35   $1,025.40