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	$97.61	13.827%	$111.1065	$111.11	$111.10	$111.10
Purchase #2	$81.43	5.548%	$85.9477	$85.95	$85.95	$85.90
Purchase #3	$153.57	7.518%	$165.1154	$165.12	$165.10	$165.10
Purchase #4	$223.42	3.346%	$230.8956	$230.90	$230.90	$230.90
Purchase #5	$163.69	3.636%	$169.6418	$169.64	$169.65	$169.60
Purchase #6	$17.82	9.138%	$19.4484	$19.45	$19.45	$19.40
Purchase #7	$78.70	9.755%	$86.3772	$86.38	$86.40	$86.40
7 purchase totals =	$816.24		$868.5326	$868.55	$868.55	$868.40