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	$41.73	10.605%	$46.1555	$46.16	$46.15	$46.20
Purchase #2	$168.40	10.239%	$185.6425	$185.64	$185.65	$185.60
Purchase #3	$30.62	10.369%	$33.795	$33.80	$33.80	$33.80
Purchase #4	$21.99	3.233%	$22.7009	$22.70	$22.70	$22.70
Purchase #5	$101.33	4.196%	$105.5818	$105.58	$105.60	$105.60
Purchase #6	$234.69	8.258%	$254.0707	$254.07	$254.05	$254.10
Purchase #7	$167.95	10.238%	$185.1447	$185.14	$185.15	$185.10
7 purchase totals =	$766.71		$833.0911	$833.09	$833.10	$833.10