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	$41.48	4.757%	$43.4532	$43.45	$43.45	$43.50
Purchase #2	$9.60	10.864%	$10.6429	$10.64	$10.65	$10.60
Purchase #3	$112.83	13.261%	$127.7924	$127.79	$127.80	$127.80
Purchase #4	$104.69	5.430%	$110.3747	$110.37	$110.35	$110.40
Purchase #5	$62.83	11.373%	$69.9757	$69.98	$70.00	$70.00
Purchase #6	$114.76	3.135%	$118.3577	$118.36	$118.35	$118.40
Purchase #7	$89.84	8.231%	$97.2347	$97.23	$97.25	$97.20
7 purchase totals =	$536.03		$577.8313	$577.82	$577.85	$577.90