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	$88.36	8.628%	$95.9837	$95.98	$96.00	$96.00
Purchase #2	$36.82	10.850%	$40.815	$40.82	$40.80	$40.80
Purchase #3	$10.70	3.776%	$11.104	$11.10	$11.10	$11.10
Purchase #4	$154.92	7.643%	$166.7605	$166.76	$166.75	$166.80
Purchase #5	$250.76	4.153%	$261.1741	$261.17	$261.15	$261.20
Purchase #6	$139.65	13.589%	$158.627	$158.63	$158.65	$158.60
Purchase #7	$95.68	4.809%	$100.2813	$100.28	$100.30	$100.30
7 purchase totals =	$776.89		$834.7456	$834.74	$834.75	$834.80