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	$214.62	5.692%	$226.8362	$226.84	$226.85	$226.80
Purchase #2	$182.88	7.451%	$196.5064	$196.51	$196.50	$196.50
Purchase #3	$11.85	5.364%	$12.4856	$12.49	$12.50	$12.50
Purchase #4	$159.30	8.522%	$172.8755	$172.88	$172.90	$172.90
Purchase #5	$120.35	3.352%	$124.3841	$124.38	$124.40	$124.40
Purchase #6	$57.89	12.821%	$65.3121	$65.31	$65.30	$65.30
Purchase #7	$19.81	9.266%	$21.6456	$21.65	$21.65	$21.60
7 purchase totals =	$766.70		$820.0455	$820.06	$820.10	$820.00