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	$202.85	5.514%	$214.0351	$214.04	$214.05	$214.00
Purchase #2	$56.85	8.649%	$61.767	$61.77	$61.75	$61.80
Purchase #3	$203.75	3.743%	$211.3764	$211.38	$211.40	$211.40
Purchase #4	$238.87	4.274%	$249.0793	$249.08	$249.10	$249.10
Purchase #5	$120.92	5.517%	$127.5912	$127.59	$127.60	$127.60
Purchase #6	$29.78	11.856%	$33.3107	$33.31	$33.30	$33.30
Purchase #7	$55.80	6.867%	$59.6318	$59.63	$59.65	$59.60
7 purchase totals =	$908.82		$956.7915	$956.80	$956.85	$956.80