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	$49.41	6.824%	$52.7817	$52.78	$52.80	$52.80
Purchase #2	$40.90	7.143%	$43.8215	$43.82	$43.80	$43.80
Purchase #3	$241.88	3.654%	$250.7183	$250.72	$250.70	$250.70
Purchase #4	$54.52	11.226%	$60.6404	$60.64	$60.65	$60.60
Purchase #5	$70.59	13.471%	$80.0992	$80.10	$80.10	$80.10
Purchase #6	$155.94	7.472%	$167.5918	$167.59	$167.60	$167.60
Purchase #7	$78.99	5.146%	$83.0548	$83.05	$83.05	$83.10
7 purchase totals =	$692.23		$738.7077	$738.70	$738.70	$738.70