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	$103.52	3.490%	$107.1328	$107.13	$107.15	$107.10
Purchase #2	$106.43	4.819%	$111.5589	$111.56	$111.55	$111.60
Purchase #3	$59.60	13.739%	$67.7884	$67.79	$67.80	$67.80
Purchase #4	$76.51	9.343%	$83.6583	$83.66	$83.65	$83.70
Purchase #5	$164.36	13.430%	$186.4335	$186.43	$186.45	$186.40
Purchase #6	$220.39	3.129%	$227.286	$227.29	$227.30	$227.30
Purchase #7	$52.54	12.414%	$59.0623	$59.06	$59.05	$59.10
7 purchase totals =	$783.35		$842.9202	$842.92	$842.95	$843.00