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	$159.88	4.243%	$166.6637	$166.66	$166.65	$166.70
Purchase #2	$217.51	8.392%	$235.7634	$235.76	$235.75	$235.80
Purchase #3	$238.71	9.857%	$262.2396	$262.24	$262.25	$262.20
Purchase #4	$82.79	11.870%	$92.6172	$92.62	$92.60	$92.60
Purchase #5	$149.51	10.466%	$165.1577	$165.16	$165.15	$165.20
Purchase #6	$35.59	7.164%	$38.1397	$38.14	$38.15	$38.10
Purchase #7	$224.53	5.122%	$236.0304	$236.03	$236.05	$236.00
7 purchase totals =	$1,108.52		$1,196.6117	$1,196.61	$1,196.60	$1,196.60