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	$117.72	7.269%	$126.2771	$126.28	$126.30	$126.30
Purchase #2	$106.88	4.415%	$111.5988	$111.60	$111.60	$111.60
Purchase #3	$62.40	11.557%	$69.6116	$69.61	$69.60	$69.60
Purchase #4	$172.87	11.868%	$193.3862	$193.39	$193.40	$193.40
Purchase #5	$189.84	8.107%	$205.2303	$205.23	$205.25	$205.20
Purchase #6	$196.64	7.558%	$211.5021	$211.50	$211.50	$211.50
Purchase #7	$141.83	3.312%	$146.5274	$146.53	$146.55	$146.50
7 purchase totals =	$988.18		$1,064.1335	$1,064.14	$1,064.20	$1,064.10