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	$86.94	5.564%	$91.7773	$91.78	$91.80	$91.80
Purchase #2	$100.69	10.537%	$111.2997	$111.30	$111.30	$111.30
Purchase #3	$15.30	6.338%	$16.2697	$16.27	$16.25	$16.30
Purchase #4	$131.60	11.154%	$146.2787	$146.28	$146.30	$146.30
Purchase #5	$128.71	3.162%	$132.7798	$132.78	$132.80	$132.80
Purchase #6	$17.39	8.462%	$18.8615	$18.86	$18.85	$18.90
Purchase #7	$175.93	7.585%	$189.2743	$189.27	$189.25	$189.30
7 purchase totals =	$656.56		$706.5410	$706.54	$706.55	$706.70