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	$80.55	4.685%	$84.3238	$84.32	$84.30	$84.30
Purchase #2	$141.35	10.262%	$155.8553	$155.86	$155.85	$155.90
Purchase #3	$73.46	5.401%	$77.4276	$77.43	$77.45	$77.40
Purchase #4	$35.98	3.675%	$37.3023	$37.30	$37.30	$37.30
Purchase #5	$149.30	8.200%	$161.5426	$161.54	$161.55	$161.50
Purchase #6	$57.48	13.837%	$65.4335	$65.43	$65.45	$65.40
Purchase #7	$161.70	6.584%	$172.3463	$172.35	$172.35	$172.30
7 purchase totals =	$699.82		$754.2314	$754.23	$754.25	$754.10