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	$160.49	7.779%	$172.9745	$172.97	$172.95	$173.00
Purchase #2	$118.67	7.177%	$127.1869	$127.19	$127.20	$127.20
Purchase #3	$18.31	11.124%	$20.3468	$20.35	$20.35	$20.30
Purchase #4	$233.33	5.225%	$245.5215	$245.52	$245.50	$245.50
Purchase #5	$155.34	7.557%	$167.079	$167.08	$167.10	$167.10
Purchase #6	$241.28	12.738%	$272.0142	$272.01	$272.00	$272.00
Purchase #7	$99.54	3.447%	$102.9711	$102.97	$102.95	$103.00
7 purchase totals =	$1,026.96		$1,108.0940	$1,108.09	$1,108.05	$1,108.10