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	$207.27	12.497%	$233.1725	$233.17	$233.15	$233.20
Purchase #2	$28.98	13.643%	$32.9337	$32.93	$32.95	$32.90
Purchase #3	$13.89	4.794%	$14.5559	$14.56	$14.55	$14.60
Purchase #4	$27.37	3.113%	$28.222	$28.22	$28.20	$28.20
Purchase #5	$142.44	9.234%	$155.5929	$155.59	$155.60	$155.60
Purchase #6	$111.37	5.628%	$117.6379	$117.64	$117.65	$117.60
Purchase #7	$89.97	10.839%	$99.7218	$99.72	$99.70	$99.70
7 purchase totals =	$621.29		$681.8367	$681.83	$681.80	$681.80