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	$115.76	10.257%	$127.6335	$127.63	$127.65	$127.60
Purchase #2	$6.82	11.671%	$7.616	$7.62	$7.60	$7.60
Purchase #3	$123.77	10.730%	$137.0505	$137.05	$137.05	$137.10
Purchase #4	$53.61	11.767%	$59.9183	$59.92	$59.90	$59.90
Purchase #5	$27.32	6.366%	$29.0592	$29.06	$29.05	$29.10
Purchase #6	$86.29	8.791%	$93.8758	$93.88	$93.90	$93.90
Purchase #7	$49.47	7.194%	$53.0289	$53.03	$53.05	$53.00
7 purchase totals =	$463.04		$508.1822	$508.19	$508.20	$508.20