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	$231.26	11.856%	$258.6782	$258.68	$258.70	$258.70
Purchase #2	$191.71	7.240%	$205.5898	$205.59	$205.60	$205.60
Purchase #3	$241.63	3.791%	$250.7902	$250.79	$250.80	$250.80
Purchase #4	$176.79	4.700%	$185.0991	$185.10	$185.10	$185.10
Purchase #5	$115.71	10.352%	$127.6883	$127.69	$127.70	$127.70
Purchase #6	$167.64	8.463%	$181.8274	$181.83	$181.85	$181.80
Purchase #7	$233.73	9.357%	$255.6001	$255.60	$255.60	$255.60
7 purchase totals =	$1,358.47		$1,465.2731	$1,465.28	$1,465.35	$1,465.30