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	$84.41	7.152%	$90.447	$90.45	$90.45	$90.40
Purchase #2	$147.71	13.312%	$167.3732	$167.37	$167.35	$167.40
Purchase #3	$181.91	12.716%	$205.0417	$205.04	$205.05	$205.00
Purchase #4	$221.37	5.671%	$233.9239	$233.92	$233.90	$233.90
Purchase #5	$93.90	8.406%	$101.7932	$101.79	$101.80	$101.80
Purchase #6	$185.99	9.181%	$203.0657	$203.07	$203.05	$203.10
Purchase #7	$99.90	11.750%	$111.6383	$111.64	$111.65	$111.60
7 purchase totals =	$1,015.19		$1,113.2830	$1,113.28	$1,113.25	$1,113.20