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	$174.91	3.341%	$180.7537	$180.75	$180.75	$180.80
Purchase #2	$125.25	5.509%	$132.15	$132.15	$132.15	$132.20
Purchase #3	$230.37	4.444%	$240.6076	$240.61	$240.60	$240.60
Purchase #4	$42.88	10.834%	$47.5256	$47.53	$47.55	$47.50
Purchase #5	$84.65	13.532%	$96.1048	$96.10	$96.10	$96.10
Purchase #6	$249.66	3.105%	$257.4119	$257.41	$257.40	$257.40
Purchase #7	$107.31	3.499%	$111.0648	$111.06	$111.05	$111.10
7 purchase totals =	$1,015.03		$1,065.6184	$1,065.61	$1,065.60	$1,065.70