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	$52.30	10.412%	$57.7455	$57.75	$57.75	$57.70
Purchase #2	$148.54	4.436%	$155.1292	$155.13	$155.15	$155.10
Purchase #3	$62.62	13.616%	$71.1463	$71.15	$71.15	$71.10
Purchase #4	$187.45	9.265%	$204.8172	$204.82	$204.80	$204.80
Purchase #5	$157.40	5.622%	$166.249	$166.25	$166.25	$166.20
Purchase #6	$230.78	6.478%	$245.7299	$245.73	$245.75	$245.70
Purchase #7	$238.39	13.873%	$271.4618	$271.46	$271.45	$271.50
7 purchase totals =	$1,077.48		$1,172.2789	$1,172.29	$1,172.30	$1,172.10