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	$35.51	4.729%	$37.1893	$37.19	$37.20	$37.20
Purchase #2	$176.28	11.724%	$196.9471	$196.95	$196.95	$196.90
Purchase #3	$94.89	3.795%	$98.4911	$98.49	$98.50	$98.50
Purchase #4	$221.48	4.135%	$230.6382	$230.64	$230.65	$230.60
Purchase #5	$101.72	12.634%	$114.5713	$114.57	$114.55	$114.60
Purchase #6	$103.45	12.225%	$116.0968	$116.10	$116.10	$116.10
Purchase #7	$34.57	5.530%	$36.4817	$36.48	$36.50	$36.50
7 purchase totals =	$767.90		$830.4155	$830.42	$830.45	$830.40