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	$34.69	5.107%	$36.4616	$36.46	$36.45	$36.50
Purchase #2	$52.73	11.720%	$58.91	$58.91	$58.90	$58.90
Purchase #3	$220.32	4.200%	$229.5734	$229.57	$229.55	$229.60
Purchase #4	$101.97	9.194%	$111.3451	$111.35	$111.35	$111.30
Purchase #5	$78.49	13.717%	$89.2565	$89.26	$89.25	$89.30
Purchase #6	$237.61	6.120%	$252.1517	$252.15	$252.15	$252.20
Purchase #7	$150.86	11.798%	$168.6585	$168.66	$168.65	$168.70
7 purchase totals =	$876.67		$946.3568	$946.36	$946.30	$946.50