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	$110.99	6.103%	$117.7637	$117.76	$117.75	$117.80
Purchase #2	$233.91	9.152%	$255.3174	$255.32	$255.30	$255.30
Purchase #3	$72.53	3.730%	$75.2354	$75.24	$75.25	$75.20
Purchase #4	$82.32	10.286%	$90.7874	$90.79	$90.80	$90.80
Purchase #5	$59.42	4.751%	$62.243	$62.24	$62.25	$62.20
Purchase #6	$144.34	10.580%	$159.6112	$159.61	$159.60	$159.60
Purchase #7	$101.68	9.808%	$111.6528	$111.65	$111.65	$111.70
7 purchase totals =	$805.19		$872.6109	$872.61	$872.60	$872.60