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	$62.39	4.851%	$65.4165	$65.42	$65.40	$65.40
Purchase #2	$118.58	9.747%	$130.138	$130.14	$130.15	$130.10
Purchase #3	$164.67	12.671%	$185.5353	$185.54	$185.55	$185.50
Purchase #4	$143.41	4.153%	$149.3658	$149.37	$149.35	$149.40
Purchase #5	$164.89	6.756%	$176.03	$176.03	$176.05	$176.00
Purchase #6	$45.83	12.799%	$51.6958	$51.70	$51.70	$51.70
Purchase #7	$101.61	7.648%	$109.3811	$109.38	$109.40	$109.40
7 purchase totals =	$801.38		$867.5625	$867.58	$867.60	$867.50