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	$102.82	8.515%	$111.5751	$111.58	$111.60	$111.60
Purchase #2	$225.86	12.158%	$253.3201	$253.32	$253.30	$253.30
Purchase #3	$217.89	7.323%	$233.8461	$233.85	$233.85	$233.80
Purchase #4	$53.50	11.262%	$59.5252	$59.53	$59.55	$59.50
Purchase #5	$113.53	4.194%	$118.2914	$118.29	$118.30	$118.30
Purchase #6	$115.40	12.202%	$129.4811	$129.48	$129.50	$129.50
Purchase #7	$67.70	10.636%	$74.9006	$74.90	$74.90	$74.90
7 purchase totals =	$896.70		$980.9396	$980.95	$981.00	$980.90