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	$49.63	11.873%	$55.5226	$55.52	$55.50	$55.50
Purchase #2	$228.41	8.442%	$247.6924	$247.69	$247.70	$247.70
Purchase #3	$173.25	11.712%	$193.541	$193.54	$193.55	$193.50
Purchase #4	$204.77	11.205%	$227.7145	$227.71	$227.70	$227.70
Purchase #5	$166.54	11.158%	$185.1225	$185.12	$185.10	$185.10
Purchase #6	$32.75	5.550%	$34.5676	$34.57	$34.55	$34.60
Purchase #7	$181.69	10.116%	$200.0698	$200.07	$200.05	$200.10
7 purchase totals =	$1,037.04		$1,144.2304	$1,144.22	$1,144.15	$1,144.20