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	$161.60	11.528%	$180.2292	$180.23	$180.25	$180.20
Purchase #2	$100.29	11.514%	$111.8374	$111.84	$111.85	$111.80
Purchase #3	$159.30	8.235%	$172.4184	$172.42	$172.40	$172.40
Purchase #4	$172.74	7.530%	$185.7473	$185.75	$185.75	$185.70
Purchase #5	$90.91	12.379%	$102.1637	$102.16	$102.15	$102.20
Purchase #6	$99.84	5.375%	$105.2064	$105.21	$105.20	$105.20
Purchase #7	$228.87	8.311%	$247.8914	$247.89	$247.90	$247.90
7 purchase totals =	$1,013.55		$1,105.4938	$1,105.50	$1,105.50	$1,105.40