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 $184.35   8.487%   $199.9958   $200.00   $200.00   $200.00  
  Purchase #2 $115.87   8.240%   $125.4177   $125.42   $125.40   $125.40  
  Purchase #3 $203.86   7.525%   $219.2005   $219.20   $219.20   $219.20  
  Purchase #4 $41.59   10.439%   $45.9316   $45.93   $45.95   $45.90  
  Purchase #5 $199.53   4.716%   $208.9398   $208.94   $208.95   $208.90  
  Purchase #6 $163.72   10.629%   $181.1218   $181.12   $181.10   $181.10  
  Purchase #7 $32.79   4.491%   $34.2626   $34.26   $34.25   $34.30  
  7 purchase totals = $941.71       $1,014.8698   $1,014.87   $1,014.85   $1,014.80