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	$49.80	6.229%	$52.902	$52.90	$52.90	$52.90
Purchase #2	$93.40	10.438%	$103.1491	$103.15	$103.15	$103.10
Purchase #3	$54.56	8.696%	$59.3045	$59.30	$59.30	$59.30
Purchase #4	$117.31	8.659%	$127.4679	$127.47	$127.45	$127.50
Purchase #5	$111.63	7.173%	$119.6372	$119.64	$119.65	$119.60
Purchase #6	$198.93	3.344%	$205.5822	$205.58	$205.60	$205.60
Purchase #7	$185.54	9.668%	$203.478	$203.48	$203.50	$203.50
7 purchase totals =	$811.17		$871.5209	$871.52	$871.55	$871.50