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	$113.31	12.177%	$127.1078	$127.11	$127.10	$127.10
Purchase #2	$178.89	6.400%	$190.339	$190.34	$190.35	$190.30
Purchase #3	$28.61	10.133%	$31.5091	$31.51	$31.50	$31.50
Purchase #4	$152.91	11.282%	$170.1613	$170.16	$170.15	$170.20
Purchase #5	$217.49	11.416%	$242.3187	$242.32	$242.30	$242.30
Purchase #6	$105.44	5.844%	$111.6019	$111.60	$111.60	$111.60
Purchase #7	$134.26	8.508%	$145.6828	$145.68	$145.70	$145.70
7 purchase totals =	$930.91		$1,018.7206	$1,018.72	$1,018.70	$1,018.70