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	$11.38	7.131%	$12.1915	$12.19	$12.20	$12.20
Purchase #2	$71.93	12.635%	$81.0184	$81.02	$81.00	$81.00
Purchase #3	$196.40	8.370%	$212.8387	$212.84	$212.85	$212.80
Purchase #4	$182.46	4.462%	$190.6014	$190.60	$190.60	$190.60
Purchase #5	$174.37	9.426%	$190.8061	$190.81	$190.80	$190.80
Purchase #6	$247.42	7.417%	$265.7711	$265.77	$265.75	$265.80
Purchase #7	$72.65	10.435%	$80.231	$80.23	$80.25	$80.20
7 purchase totals =	$956.61		$1,033.4582	$1,033.46	$1,033.45	$1,033.40