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	$237.25	7.624%	$255.3379	$255.34	$255.35	$255.30
Purchase #2	$89.75	3.251%	$92.6678	$92.67	$92.65	$92.70
Purchase #3	$139.64	8.327%	$151.2678	$151.27	$151.25	$151.30
Purchase #4	$186.27	4.348%	$194.369	$194.37	$194.35	$194.40
Purchase #5	$143.25	13.615%	$162.7535	$162.75	$162.75	$162.80
Purchase #6	$58.89	9.312%	$64.3738	$64.37	$64.35	$64.40
Purchase #7	$214.89	9.486%	$235.2745	$235.27	$235.25	$235.30
7 purchase totals =	$1,069.94		$1,156.0443	$1,156.04	$1,155.95	$1,156.20