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	$40.87	3.314%	$42.2244	$42.22	$42.20	$42.20
Purchase #2	$136.31	5.823%	$144.2473	$144.25	$144.25	$144.20
Purchase #3	$18.80	5.423%	$19.8195	$19.82	$19.80	$19.80
Purchase #4	$207.82	4.865%	$217.9304	$217.93	$217.95	$217.90
Purchase #5	$132.36	13.142%	$149.7548	$149.75	$149.75	$149.80
Purchase #6	$115.37	10.196%	$127.1331	$127.13	$127.15	$127.10
Purchase #7	$199.73	9.577%	$218.8581	$218.86	$218.85	$218.90
7 purchase totals =	$851.26		$919.9676	$919.96	$919.95	$919.90