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	$179.78	9.445%	$196.7602	$196.76	$196.75	$196.80
Purchase #2	$129.80	10.595%	$143.5523	$143.55	$143.55	$143.60
Purchase #3	$240.90	3.481%	$249.2857	$249.29	$249.30	$249.30
Purchase #4	$129.36	13.324%	$146.5959	$146.60	$146.60	$146.60
Purchase #5	$110.74	6.711%	$118.1718	$118.17	$118.15	$118.20
Purchase #6	$171.42	13.509%	$194.5771	$194.58	$194.60	$194.60
Purchase #7	$142.51	13.756%	$162.1137	$162.11	$162.10	$162.10
7 purchase totals =	$1,104.51		$1,211.0567	$1,211.06	$1,211.05	$1,211.20