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	$99.32	11.419%	$110.6614	$110.66	$110.65	$110.70
Purchase #2	$166.77	10.823%	$184.8195	$184.82	$184.80	$184.80
Purchase #3	$154.62	10.578%	$170.9757	$170.98	$171.00	$171.00
Purchase #4	$129.39	3.816%	$134.3275	$134.33	$134.35	$134.30
Purchase #5	$29.32	8.675%	$31.8635	$31.86	$31.85	$31.90
Purchase #6	$42.47	9.534%	$46.5191	$46.52	$46.50	$46.50
Purchase #7	$41.76	9.142%	$45.5777	$45.58	$45.60	$45.60
7 purchase totals =	$663.65		$724.7444	$724.75	$724.75	$724.80