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	$233.90	12.272%	$262.6042	$262.60	$262.60	$262.60
Purchase #2	$58.53	11.301%	$65.1445	$65.14	$65.15	$65.10
Purchase #3	$71.83	12.286%	$80.655	$80.66	$80.65	$80.70
Purchase #4	$131.68	11.766%	$147.1735	$147.17	$147.15	$147.20
Purchase #5	$121.73	12.667%	$137.1495	$137.15	$137.15	$137.10
Purchase #6	$132.60	12.461%	$149.1233	$149.12	$149.10	$149.10
Purchase #7	$158.55	10.128%	$174.6079	$174.61	$174.60	$174.60
7 purchase totals =	$908.82		$1,016.4579	$1,016.45	$1,016.40	$1,016.40