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	$118.85	5.587%	$125.4901	$125.49	$125.50	$125.50
Purchase #2	$196.73	10.415%	$217.2194	$217.22	$217.20	$217.20
Purchase #3	$158.32	6.159%	$168.0709	$168.07	$168.05	$168.10
Purchase #4	$145.54	4.180%	$151.6236	$151.62	$151.60	$151.60
Purchase #5	$206.78	11.255%	$230.0531	$230.05	$230.05	$230.10
Purchase #6	$99.35	12.680%	$111.9476	$111.95	$111.95	$111.90
Purchase #7	$30.35	3.517%	$31.4174	$31.42	$31.40	$31.40
7 purchase totals =	$955.92		$1,035.8221	$1,035.82	$1,035.75	$1,035.80