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	$57.45	8.150%	$62.1322	$62.13	$62.15	$62.10
Purchase #2	$128.77	12.856%	$145.3247	$145.32	$145.30	$145.30
Purchase #3	$60.63	13.215%	$68.6423	$68.64	$68.65	$68.60
Purchase #4	$191.56	13.675%	$217.7558	$217.76	$217.75	$217.80
Purchase #5	$247.49	4.498%	$258.6221	$258.62	$258.60	$258.60
Purchase #6	$33.52	4.570%	$35.0519	$35.05	$35.05	$35.10
Purchase #7	$249.91	11.823%	$279.4569	$279.46	$279.45	$279.50
7 purchase totals =	$969.33		$1,066.9859	$1,066.98	$1,066.95	$1,067.00