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	$83.85	8.486%	$90.9655	$90.97	$90.95	$91.00
Purchase #2	$36.35	3.198%	$37.5125	$37.51	$37.50	$37.50
Purchase #3	$11.67	13.731%	$13.2724	$13.27	$13.25	$13.30
Purchase #4	$182.72	8.576%	$198.3901	$198.39	$198.40	$198.40
Purchase #5	$241.35	4.650%	$252.5728	$252.57	$252.55	$252.60
Purchase #6	$88.40	10.389%	$97.5839	$97.58	$97.60	$97.60
Purchase #7	$128.99	10.262%	$142.227	$142.23	$142.25	$142.20
7 purchase totals =	$773.33		$832.5242	$832.52	$832.50	$832.60