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	$48.29	8.580%	$52.4333	$52.43	$52.45	$52.40
Purchase #2	$90.60	8.867%	$98.6335	$98.63	$98.65	$98.60
Purchase #3	$65.67	10.504%	$72.568	$72.57	$72.55	$72.60
Purchase #4	$101.67	9.301%	$111.1263	$111.13	$111.15	$111.10
Purchase #5	$64.25	9.354%	$70.2599	$70.26	$70.25	$70.30
Purchase #6	$29.71	8.133%	$32.1263	$32.13	$32.15	$32.10
Purchase #7	$166.65	12.259%	$187.0796	$187.08	$187.10	$187.10
7 purchase totals =	$566.84		$624.2269	$624.23	$624.30	$624.20