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	$166.93	11.153%	$185.5477	$185.55	$185.55	$185.50
Purchase #2	$103.65	10.560%	$114.5954	$114.60	$114.60	$114.60
Purchase #3	$113.58	7.583%	$122.1928	$122.19	$122.20	$122.20
Purchase #4	$112.47	3.553%	$116.4661	$116.47	$116.45	$116.50
Purchase #5	$38.97	11.146%	$43.3136	$43.31	$43.30	$43.30
Purchase #6	$162.45	5.714%	$171.7324	$171.73	$171.75	$171.70
Purchase #7	$154.50	11.589%	$172.405	$172.41	$172.40	$172.40
7 purchase totals =	$852.55		$926.2530	$926.26	$926.25	$926.20