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	$201.34	13.867%	$229.2598	$229.26	$229.25	$229.30
Purchase #2	$147.83	5.613%	$156.1277	$156.13	$156.15	$156.10
Purchase #3	$28.27	11.793%	$31.6039	$31.60	$31.60	$31.60
Purchase #4	$221.97	13.208%	$251.2878	$251.29	$251.30	$251.30
Purchase #5	$65.44	10.614%	$72.3858	$72.39	$72.40	$72.40
Purchase #6	$103.94	11.739%	$116.1415	$116.14	$116.15	$116.10
Purchase #7	$102.28	8.808%	$111.2888	$111.29	$111.30	$111.30
7 purchase totals =	$871.07		$968.0953	$968.10	$968.15	$968.10