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	$76.28	11.603%	$85.1308	$85.13	$85.15	$85.10
Purchase #2	$118.42	4.572%	$123.8342	$123.83	$123.85	$123.80
Purchase #3	$94.65	11.830%	$105.8471	$105.85	$105.85	$105.80
Purchase #4	$221.49	6.663%	$236.2479	$236.25	$236.25	$236.20
Purchase #5	$183.58	10.429%	$202.7256	$202.73	$202.75	$202.70
Purchase #6	$84.25	7.735%	$90.7667	$90.77	$90.75	$90.80
Purchase #7	$46.59	12.734%	$52.5228	$52.52	$52.50	$52.50
7 purchase totals =	$825.26		$897.0751	$897.08	$897.10	$896.90