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	$56.75	4.569%	$59.3429	$59.34	$59.35	$59.30
Purchase #2	$115.79	10.129%	$127.5184	$127.52	$127.50	$127.50
Purchase #3	$73.97	12.136%	$82.947	$82.95	$82.95	$82.90
Purchase #4	$130.49	3.105%	$134.5417	$134.54	$134.55	$134.50
Purchase #5	$58.77	9.292%	$64.2309	$64.23	$64.25	$64.20
Purchase #6	$118.83	7.211%	$127.3988	$127.40	$127.40	$127.40
Purchase #7	$199.55	5.281%	$210.0882	$210.09	$210.10	$210.10
7 purchase totals =	$754.15		$806.0679	$806.07	$806.10	$805.90