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	$182.50	5.120%	$191.844	$191.84	$191.85	$191.80
Purchase #2	$39.71	12.801%	$44.7933	$44.79	$44.80	$44.80
Purchase #3	$249.58	3.677%	$258.7571	$258.76	$258.75	$258.80
Purchase #4	$210.42	12.714%	$237.1728	$237.17	$237.15	$237.20
Purchase #5	$160.43	7.739%	$172.8457	$172.85	$172.85	$172.80
Purchase #6	$79.84	12.321%	$89.6771	$89.68	$89.70	$89.70
Purchase #7	$21.49	4.370%	$22.4291	$22.43	$22.45	$22.40
7 purchase totals =	$943.97		$1,017.5191	$1,017.52	$1,017.55	$1,017.50