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	$228.41	11.858%	$255.4949	$255.49	$255.50	$255.50
Purchase #2	$238.47	4.479%	$249.1511	$249.15	$249.15	$249.20
Purchase #3	$91.44	11.808%	$102.2372	$102.24	$102.25	$102.20
Purchase #4	$122.45	12.116%	$137.286	$137.29	$137.30	$137.30
Purchase #5	$56.68	10.742%	$62.7686	$62.77	$62.75	$62.80
Purchase #6	$157.62	10.474%	$174.1291	$174.13	$174.15	$174.10
Purchase #7	$185.89	5.734%	$196.5489	$196.55	$196.55	$196.50
7 purchase totals =	$1,080.96		$1,177.6158	$1,177.62	$1,177.65	$1,177.60