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	$136.54	11.120%	$151.7232	$151.72	$151.70	$151.70
Purchase #2	$138.26	11.632%	$154.3424	$154.34	$154.35	$154.30
Purchase #3	$64.63	9.736%	$70.9224	$70.92	$70.90	$70.90
Purchase #4	$56.52	10.485%	$62.4461	$62.45	$62.45	$62.40
Purchase #5	$121.40	9.625%	$133.0848	$133.08	$133.10	$133.10
Purchase #6	$18.39	5.564%	$19.4132	$19.41	$19.40	$19.40
Purchase #7	$90.37	11.636%	$100.8855	$100.89	$100.90	$100.90
7 purchase totals =	$626.11		$692.8176	$692.81	$692.80	$692.70