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	$59.25	12.625%	$66.7303	$66.73	$66.75	$66.70
Purchase #2	$235.49	9.249%	$257.2705	$257.27	$257.25	$257.30
Purchase #3	$89.99	10.209%	$99.1771	$99.18	$99.20	$99.20
Purchase #4	$227.83	4.102%	$237.1756	$237.18	$237.20	$237.20
Purchase #5	$97.49	6.488%	$103.8152	$103.82	$103.80	$103.80
Purchase #6	$66.50	5.829%	$70.3763	$70.38	$70.40	$70.40
Purchase #7	$119.65	6.421%	$127.3327	$127.33	$127.35	$127.30
7 purchase totals =	$896.20		$961.8777	$961.89	$961.95	$961.90