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	$166.81	7.363%	$179.0922	$179.09	$179.10	$179.10
Purchase #2	$11.99	5.515%	$12.6512	$12.65	$12.65	$12.70
Purchase #3	$114.57	11.230%	$127.4362	$127.44	$127.45	$127.40
Purchase #4	$105.29	11.550%	$117.451	$117.45	$117.45	$117.50
Purchase #5	$84.29	13.394%	$95.5798	$95.58	$95.60	$95.60
Purchase #6	$179.75	11.365%	$200.1786	$200.18	$200.20	$200.20
Purchase #7	$172.42	11.230%	$191.7828	$191.78	$191.80	$191.80
7 purchase totals =	$835.12		$924.1718	$924.17	$924.25	$924.30