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	$206.45	11.377%	$229.9378	$229.94	$229.95	$229.90
Purchase #2	$91.45	9.773%	$100.3874	$100.39	$100.40	$100.40
Purchase #3	$107.97	10.243%	$119.0294	$119.03	$119.05	$119.00
Purchase #4	$107.69	3.174%	$111.1081	$111.11	$111.10	$111.10
Purchase #5	$122.94	3.842%	$127.6634	$127.66	$127.65	$127.70
Purchase #6	$12.98	8.693%	$14.1084	$14.11	$14.10	$14.10
Purchase #7	$101.80	9.554%	$111.526	$111.53	$111.55	$111.50
7 purchase totals =	$751.28		$813.7605	$813.77	$813.80	$813.70