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	$199.45	5.833%	$211.0839	$211.08	$211.10	$211.10
Purchase #2	$98.65	11.123%	$109.6228	$109.62	$109.60	$109.60
Purchase #3	$99.44	12.285%	$111.6562	$111.66	$111.65	$111.70
Purchase #4	$65.60	13.523%	$74.4711	$74.47	$74.45	$74.50
Purchase #5	$211.26	6.781%	$225.5855	$225.59	$225.60	$225.60
Purchase #6	$195.47	6.251%	$207.6888	$207.69	$207.70	$207.70
Purchase #7	$59.52	5.158%	$62.59	$62.59	$62.60	$62.60
7 purchase totals =	$929.39		$1,002.6983	$1,002.70	$1,002.70	$1,002.80