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	$105.75	5.398%	$111.4584	$111.46	$111.45	$111.50
Purchase #2	$70.89	4.718%	$74.2346	$74.23	$74.25	$74.20
Purchase #3	$27.98	6.682%	$29.8496	$29.85	$29.85	$29.80
Purchase #4	$49.62	6.304%	$52.748	$52.75	$52.75	$52.70
Purchase #5	$96.27	13.201%	$108.9786	$108.98	$109.00	$109.00
Purchase #6	$59.95	3.449%	$62.0177	$62.02	$62.00	$62.00
Purchase #7	$116.91	9.430%	$127.9346	$127.93	$127.95	$127.90
7 purchase totals =	$527.37		$567.2215	$567.22	$567.25	$567.10