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	$153.86	5.298%	$162.0115	$162.01	$162.00	$162.00
Purchase #2	$113.52	8.863%	$123.5813	$123.58	$123.60	$123.60
Purchase #3	$73.34	10.839%	$81.2893	$81.29	$81.30	$81.30
Purchase #4	$63.30	12.501%	$71.2131	$71.21	$71.20	$71.20
Purchase #5	$179.87	10.434%	$198.6376	$198.64	$198.65	$198.60
Purchase #6	$211.70	9.784%	$232.4127	$232.41	$232.40	$232.40
Purchase #7	$40.77	10.583%	$45.0847	$45.08	$45.10	$45.10
7 purchase totals =	$836.36		$914.2302	$914.22	$914.25	$914.20