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	$164.66	3.314%	$170.1168	$170.12	$170.10	$170.10
Purchase #2	$172.71	8.387%	$187.1952	$187.20	$187.20	$187.20
Purchase #3	$54.92	3.634%	$56.9158	$56.92	$56.90	$56.90
Purchase #4	$59.39	9.670%	$65.133	$65.13	$65.15	$65.10
Purchase #5	$121.34	5.341%	$127.8208	$127.82	$127.80	$127.80
Purchase #6	$156.56	10.774%	$173.4278	$173.43	$173.45	$173.40
Purchase #7	$131.80	9.502%	$144.3236	$144.32	$144.30	$144.30
7 purchase totals =	$861.38		$924.9330	$924.94	$924.90	$924.80