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	$112.83	11.847%	$126.197	$126.20	$126.20	$126.20
Purchase #2	$54.96	13.786%	$62.5368	$62.54	$62.55	$62.50
Purchase #3	$29.62	13.146%	$33.5138	$33.51	$33.50	$33.50
Purchase #4	$35.60	6.292%	$37.84	$37.84	$37.85	$37.80
Purchase #5	$95.80	11.764%	$107.0699	$107.07	$107.05	$107.10
Purchase #6	$85.29	6.485%	$90.8211	$90.82	$90.80	$90.80
Purchase #7	$247.67	11.627%	$276.4666	$276.47	$276.45	$276.50
7 purchase totals =	$661.77		$734.4452	$734.45	$734.40	$734.40