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	$120.26	6.133%	$127.6355	$127.64	$127.65	$127.60
Purchase #2	$24.31	12.833%	$27.4297	$27.43	$27.45	$27.40
Purchase #3	$216.98	3.205%	$223.9342	$223.93	$223.95	$223.90
Purchase #4	$145.59	10.127%	$160.3339	$160.33	$160.35	$160.30
Purchase #5	$178.63	7.125%	$191.3574	$191.36	$191.35	$191.40
Purchase #6	$222.32	7.312%	$238.576	$238.58	$238.60	$238.60
Purchase #7	$74.95	3.169%	$77.3252	$77.33	$77.35	$77.30
7 purchase totals =	$983.04		$1,046.5919	$1,046.60	$1,046.70	$1,046.50