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	$228.64	12.806%	$257.9196	$257.92	$257.90	$257.90
Purchase #2	$144.43	3.157%	$148.9897	$148.99	$149.00	$149.00
Purchase #3	$137.26	6.574%	$146.2835	$146.28	$146.30	$146.30
Purchase #4	$98.96	12.725%	$111.5527	$111.55	$111.55	$111.60
Purchase #5	$47.79	3.618%	$49.519	$49.52	$49.50	$49.50
Purchase #6	$93.72	12.410%	$105.3507	$105.35	$105.35	$105.40
Purchase #7	$100.70	12.745%	$113.5342	$113.53	$113.55	$113.50
7 purchase totals =	$851.50		$933.1494	$933.14	$933.15	$933.20