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	$211.27	4.666%	$221.1279	$221.13	$221.15	$221.10
Purchase #2	$97.78	7.827%	$105.4332	$105.43	$105.45	$105.40
Purchase #3	$45.79	6.227%	$48.6413	$48.64	$48.65	$48.60
Purchase #4	$245.37	3.167%	$253.1409	$253.14	$253.15	$253.10
Purchase #5	$145.42	10.298%	$160.3954	$160.40	$160.40	$160.40
Purchase #6	$250.50	8.704%	$272.3035	$272.30	$272.30	$272.30
Purchase #7	$117.83	5.104%	$123.844	$123.84	$123.85	$123.80
7 purchase totals =	$1,113.96		$1,184.8862	$1,184.88	$1,184.95	$1,184.70