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	$178.84	6.848%	$191.087	$191.09	$191.10	$191.10
Purchase #2	$228.52	5.823%	$241.8267	$241.83	$241.85	$241.80
Purchase #3	$247.82	3.516%	$256.5334	$256.53	$256.55	$256.50
Purchase #4	$191.80	3.829%	$199.144	$199.14	$199.15	$199.10
Purchase #5	$49.67	4.783%	$52.0457	$52.05	$52.05	$52.00
Purchase #6	$48.87	11.495%	$54.4876	$54.49	$54.50	$54.50
Purchase #7	$171.76	11.543%	$191.5863	$191.59	$191.60	$191.60
7 purchase totals =	$1,117.28		$1,186.7107	$1,186.72	$1,186.80	$1,186.60