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	$168.64	7.363%	$181.057	$181.06	$181.05	$181.10
Purchase #2	$85.34	11.142%	$94.8486	$94.85	$94.85	$94.80
Purchase #3	$67.51	7.399%	$72.5051	$72.51	$72.50	$72.50
Purchase #4	$151.66	7.801%	$163.491	$163.49	$163.50	$163.50
Purchase #5	$119.86	6.469%	$127.6137	$127.61	$127.60	$127.60
Purchase #6	$160.75	3.866%	$166.9646	$166.96	$166.95	$167.00
Purchase #7	$53.94	5.207%	$56.7487	$56.75	$56.75	$56.70
7 purchase totals =	$807.70		$863.2287	$863.23	$863.20	$863.20