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	$49.42	9.496%	$54.1129	$54.11	$54.10	$54.10
Purchase #2	$48.90	9.541%	$53.5655	$53.57	$53.55	$53.60
Purchase #3	$196.71	4.555%	$205.6701	$205.67	$205.65	$205.70
Purchase #4	$211.71	5.149%	$222.6109	$222.61	$222.60	$222.60
Purchase #5	$164.95	4.566%	$172.4816	$172.48	$172.50	$172.50
Purchase #6	$121.36	4.852%	$127.2484	$127.25	$127.25	$127.20
Purchase #7	$170.35	10.109%	$187.5707	$187.57	$187.55	$187.60
7 purchase totals =	$963.40		$1,023.2601	$1,023.26	$1,023.20	$1,023.30