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	$141.45	10.683%	$156.5611	$156.56	$156.55	$156.60
Purchase #2	$52.59	7.263%	$56.4096	$56.41	$56.40	$56.40
Purchase #3	$93.89	3.251%	$96.9424	$96.94	$96.95	$96.90
Purchase #4	$145.91	5.572%	$154.0401	$154.04	$154.05	$154.00
Purchase #5	$132.42	9.236%	$144.6503	$144.65	$144.65	$144.70
Purchase #6	$243.60	4.760%	$255.1954	$255.20	$255.20	$255.20
Purchase #7	$228.80	13.315%	$259.2647	$259.26	$259.25	$259.30
7 purchase totals =	$1,038.66		$1,123.0636	$1,123.06	$1,123.05	$1,123.10