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	$101.64	9.799%	$111.5997	$111.60	$111.60	$111.60
Purchase #2	$18.55	12.247%	$20.8218	$20.82	$20.80	$20.80
Purchase #3	$193.65	7.450%	$208.0769	$208.08	$208.10	$208.10
Purchase #4	$244.50	12.584%	$275.2679	$275.27	$275.25	$275.30
Purchase #5	$164.66	7.763%	$177.4426	$177.44	$177.45	$177.40
Purchase #6	$160.50	7.555%	$172.6258	$172.63	$172.65	$172.60
Purchase #7	$47.34	10.419%	$52.2724	$52.27	$52.25	$52.30
7 purchase totals =	$930.84		$1,018.1071	$1,018.11	$1,018.10	$1,018.10