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	$138.40	3.381%	$143.0793	$143.08	$143.10	$143.10
Purchase #2	$154.54	12.288%	$173.5299	$173.53	$173.55	$173.50
Purchase #3	$136.74	12.274%	$153.5235	$153.52	$153.50	$153.50
Purchase #4	$33.93	10.380%	$37.4519	$37.45	$37.45	$37.50
Purchase #5	$37.40	5.617%	$39.5008	$39.50	$39.50	$39.50
Purchase #6	$57.61	5.224%	$60.6195	$60.62	$60.60	$60.60
Purchase #7	$95.33	4.737%	$99.8458	$99.85	$99.85	$99.80
7 purchase totals =	$653.95		$707.5507	$707.55	$707.55	$707.50