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	$101.81	9.832%	$111.82	$111.82	$111.80	$111.80
Purchase #2	$210.40	11.168%	$233.8975	$233.90	$233.90	$233.90
Purchase #3	$8.84	4.455%	$9.2338	$9.23	$9.25	$9.20
Purchase #4	$192.25	4.260%	$200.4399	$200.44	$200.45	$200.40
Purchase #5	$149.27	5.582%	$157.6023	$157.60	$157.60	$157.60
Purchase #6	$216.58	10.830%	$240.0356	$240.04	$240.05	$240.00
Purchase #7	$192.48	6.712%	$205.3993	$205.40	$205.40	$205.40
7 purchase totals =	$1,071.63		$1,158.4284	$1,158.43	$1,158.45	$1,158.30