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	$53.69	5.640%	$56.7181	$56.72	$56.70	$56.70
Purchase #2	$214.74	6.714%	$229.1576	$229.16	$229.15	$229.20
Purchase #3	$113.35	9.182%	$123.7578	$123.76	$123.75	$123.80
Purchase #4	$238.40	6.421%	$253.7077	$253.71	$253.70	$253.70
Purchase #5	$115.76	10.211%	$127.5803	$127.58	$127.60	$127.60
Purchase #6	$240.26	13.801%	$273.4183	$273.42	$273.40	$273.40
Purchase #7	$19.68	6.868%	$21.0316	$21.03	$21.05	$21.00
7 purchase totals =	$995.88		$1,085.3714	$1,085.38	$1,085.35	$1,085.40