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 $186.46   9.764%   $204.666   $204.67   $204.65   $204.70  
  Purchase #2 $152.94   3.264%   $157.932   $157.93   $157.95   $157.90  
  Purchase #3 $216.68   13.774%   $246.5255   $246.53   $246.55   $246.50  
  Purchase #4 $158.47   9.839%   $174.0619   $174.06   $174.05   $174.10  
  Purchase #5 $195.36   9.741%   $214.39   $214.39   $214.40   $214.40  
  Purchase #6 $187.79   3.153%   $193.711   $193.71   $193.70   $193.70  
  Purchase #7 $201.82   9.863%   $221.7255   $221.73   $221.75   $221.70  
  7 purchase totals = $1,299.52       $1,413.0119   $1,413.02   $1,413.05   $1,413.00