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	$138.78	13.807%	$157.9414	$157.94	$157.95	$157.90
Purchase #2	$32.25	11.523%	$35.9662	$35.97	$35.95	$36.00
Purchase #3	$34.62	7.648%	$37.2677	$37.27	$37.25	$37.30
Purchase #4	$74.47	3.501%	$77.0772	$77.08	$77.10	$77.10
Purchase #5	$97.74	13.662%	$111.0932	$111.09	$111.10	$111.10
Purchase #6	$142.39	10.146%	$156.8369	$156.84	$156.85	$156.80
Purchase #7	$144.45	7.539%	$155.3401	$155.34	$155.35	$155.30
7 purchase totals =	$664.70		$731.5227	$731.53	$731.55	$731.50