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	$118.60	4.172%	$123.548	$123.55	$123.55	$123.50
Purchase #2	$102.53	5.184%	$107.8452	$107.85	$107.85	$107.80
Purchase #3	$46.71	3.819%	$48.4939	$48.49	$48.50	$48.50
Purchase #4	$104.31	7.136%	$111.7536	$111.75	$111.75	$111.80
Purchase #5	$71.49	6.512%	$76.1454	$76.15	$76.15	$76.10
Purchase #6	$204.47	12.646%	$230.3273	$230.33	$230.35	$230.30
Purchase #7	$35.81	4.632%	$37.4687	$37.47	$37.45	$37.50
7 purchase totals =	$683.92		$735.5821	$735.59	$735.60	$735.50