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	$186.37	5.208%	$196.0761	$196.08	$196.10	$196.10
Purchase #2	$58.61	5.114%	$61.6073	$61.61	$61.60	$61.60
Purchase #3	$130.55	10.524%	$144.2891	$144.29	$144.30	$144.30
Purchase #4	$204.37	3.247%	$211.0059	$211.01	$211.00	$211.00
Purchase #5	$232.56	10.200%	$256.2811	$256.28	$256.30	$256.30
Purchase #6	$198.47	9.674%	$217.67	$217.67	$217.65	$217.70
Purchase #7	$230.97	10.123%	$254.3511	$254.35	$254.35	$254.40
7 purchase totals =	$1,241.90		$1,341.2806	$1,341.29	$1,341.30	$1,341.40