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	$225.84	4.127%	$235.1604	$235.16	$235.15	$235.20
Purchase #2	$145.81	11.543%	$162.6408	$162.64	$162.65	$162.60
Purchase #3	$216.96	4.746%	$227.2569	$227.26	$227.25	$227.30
Purchase #4	$48.67	10.369%	$53.7166	$53.72	$53.70	$53.70
Purchase #5	$71.45	12.559%	$80.4234	$80.42	$80.40	$80.40
Purchase #6	$173.25	10.387%	$191.2455	$191.25	$191.25	$191.20
Purchase #7	$113.68	12.724%	$128.1446	$128.14	$128.15	$128.10
7 purchase totals =	$995.66		$1,078.5882	$1,078.59	$1,078.55	$1,078.50