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	$211.92	10.679%	$234.5509	$234.55	$234.55	$234.60
Purchase #2	$9.33	9.580%	$10.2238	$10.22	$10.20	$10.20
Purchase #3	$114.29	12.584%	$128.6723	$128.67	$128.65	$128.70
Purchase #4	$163.28	6.303%	$173.5715	$173.57	$173.55	$173.60
Purchase #5	$224.89	12.641%	$253.3183	$253.32	$253.30	$253.30
Purchase #6	$205.91	6.154%	$218.5817	$218.58	$218.60	$218.60
Purchase #7	$53.77	10.179%	$59.2432	$59.24	$59.25	$59.20
7 purchase totals =	$983.39		$1,078.1617	$1,078.15	$1,078.10	$1,078.20