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	$38.32	11.221%	$42.6199	$42.62	$42.60	$42.60
Purchase #2	$46.86	12.244%	$52.5975	$52.60	$52.60	$52.60
Purchase #3	$53.37	3.587%	$55.2844	$55.28	$55.30	$55.30
Purchase #4	$181.91	3.248%	$187.8184	$187.82	$187.80	$187.80
Purchase #5	$206.69	11.438%	$230.3312	$230.33	$230.35	$230.30
Purchase #6	$154.27	10.280%	$170.129	$170.13	$170.15	$170.10
Purchase #7	$16.43	13.464%	$18.6421	$18.64	$18.65	$18.60
7 purchase totals =	$697.85		$757.4225	$757.42	$757.45	$757.30