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	$59.31	13.327%	$67.2142	$67.21	$67.20	$67.20
Purchase #2	$238.71	9.137%	$260.5209	$260.52	$260.50	$260.50
Purchase #3	$17.77	11.833%	$19.8727	$19.87	$19.85	$19.90
Purchase #4	$189.55	11.257%	$210.8876	$210.89	$210.90	$210.90
Purchase #5	$210.70	11.733%	$235.4214	$235.42	$235.40	$235.40
Purchase #6	$199.46	11.488%	$222.374	$222.37	$222.35	$222.40
Purchase #7	$57.30	5.443%	$60.4188	$60.42	$60.40	$60.40
7 purchase totals =	$972.80		$1,076.7096	$1,076.70	$1,076.60	$1,076.70