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	$231.28	12.301%	$259.7298	$259.73	$259.75	$259.70
Purchase #2	$189.51	3.699%	$196.52	$196.52	$196.50	$196.50
Purchase #3	$203.46	6.195%	$216.0643	$216.06	$216.05	$216.10
Purchase #4	$86.87	12.258%	$97.5185	$97.52	$97.50	$97.50
Purchase #5	$207.47	11.305%	$230.9245	$230.92	$230.90	$230.90
Purchase #6	$177.78	4.368%	$185.5454	$185.55	$185.55	$185.50
Purchase #7	$106.97	4.515%	$111.7997	$111.80	$111.80	$111.80
7 purchase totals =	$1,203.34		$1,298.1022	$1,298.10	$1,298.05	$1,298.00