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	$250.28	5.303%	$263.5523	$263.55	$263.55	$263.60
Purchase #2	$92.87	7.771%	$100.0869	$100.09	$100.10	$100.10
Purchase #3	$86.74	6.238%	$92.1508	$92.15	$92.15	$92.20
Purchase #4	$214.65	12.305%	$241.0627	$241.06	$241.05	$241.10
Purchase #5	$242.44	4.434%	$253.1898	$253.19	$253.20	$253.20
Purchase #6	$102.97	9.443%	$112.6935	$112.69	$112.70	$112.70
Purchase #7	$119.85	6.680%	$127.856	$127.86	$127.85	$127.90
7 purchase totals =	$1,109.80		$1,190.5920	$1,190.59	$1,190.60	$1,190.80