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	$37.42	8.130%	$40.4622	$40.46	$40.45	$40.50
Purchase #2	$46.65	4.102%	$48.5636	$48.56	$48.55	$48.60
Purchase #3	$21.93	11.869%	$24.5329	$24.53	$24.55	$24.50
Purchase #4	$79.98	6.131%	$84.8836	$84.88	$84.90	$84.90
Purchase #5	$153.98	13.858%	$175.3185	$175.32	$175.30	$175.30
Purchase #6	$196.72	13.488%	$223.2536	$223.25	$223.25	$223.30
Purchase #7	$116.61	9.293%	$127.4466	$127.45	$127.45	$127.40
7 purchase totals =	$653.29		$724.4610	$724.45	$724.45	$724.50