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	$105.95	5.220%	$111.4806	$111.48	$111.50	$111.50
Purchase #2	$243.43	8.159%	$263.2915	$263.29	$263.30	$263.30
Purchase #3	$235.33	11.579%	$262.5789	$262.58	$262.60	$262.60
Purchase #4	$145.59	13.161%	$164.7511	$164.75	$164.75	$164.80
Purchase #5	$94.31	7.215%	$101.1145	$101.11	$101.10	$101.10
Purchase #6	$128.26	3.428%	$132.6568	$132.66	$132.65	$132.70
Purchase #7	$173.88	10.224%	$191.6575	$191.66	$191.65	$191.70
7 purchase totals =	$1,126.75		$1,227.5309	$1,227.53	$1,227.55	$1,227.70