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	$56.50	9.871%	$62.0771	$62.08	$62.10	$62.10
Purchase #2	$99.93	5.236%	$105.1623	$105.16	$105.15	$105.20
Purchase #3	$108.71	13.357%	$123.2304	$123.23	$123.25	$123.20
Purchase #4	$51.39	13.756%	$58.4592	$58.46	$58.45	$58.50
Purchase #5	$30.95	12.543%	$34.8321	$34.83	$34.85	$34.80
Purchase #6	$167.37	4.139%	$174.2974	$174.30	$174.30	$174.30
Purchase #7	$124.59	6.815%	$133.0808	$133.08	$133.10	$133.10
7 purchase totals =	$639.44		$691.1393	$691.14	$691.20	$691.20