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	$62.95	6.784%	$67.2205	$67.22	$67.20	$67.20
Purchase #2	$50.44	8.514%	$54.7345	$54.73	$54.75	$54.70
Purchase #3	$153.79	5.823%	$162.7452	$162.75	$162.75	$162.70
Purchase #4	$25.72	9.868%	$28.258	$28.26	$28.25	$28.30
Purchase #5	$10.70	6.139%	$11.3569	$11.36	$11.35	$11.40
Purchase #6	$39.36	8.658%	$42.7678	$42.77	$42.75	$42.80
Purchase #7	$133.47	4.447%	$139.4054	$139.41	$139.40	$139.40
7 purchase totals =	$476.43		$506.4883	$506.50	$506.45	$506.50