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	$170.65	4.694%	$178.6603	$178.66	$178.65	$178.70
Purchase #2	$237.58	3.152%	$245.0685	$245.07	$245.05	$245.10
Purchase #3	$42.41	8.628%	$46.0691	$46.07	$46.05	$46.10
Purchase #4	$43.72	3.842%	$45.3997	$45.40	$45.40	$45.40
Purchase #5	$151.35	10.273%	$166.8982	$166.90	$166.90	$166.90
Purchase #6	$88.66	4.671%	$92.8013	$92.80	$92.80	$92.80
Purchase #7	$56.60	4.707%	$59.2642	$59.26	$59.25	$59.30
7 purchase totals =	$790.97		$834.1613	$834.16	$834.10	$834.30