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	$38.37	9.244%	$41.9169	$41.92	$41.90	$41.90
Purchase #2	$200.25	7.860%	$215.9897	$215.99	$216.00	$216.00
Purchase #3	$249.56	10.250%	$275.1399	$275.14	$275.15	$275.10
Purchase #4	$178.47	7.872%	$192.5192	$192.52	$192.50	$192.50
Purchase #5	$23.49	4.782%	$24.6133	$24.61	$24.60	$24.60
Purchase #6	$191.46	10.686%	$211.9194	$211.92	$211.90	$211.90
Purchase #7	$125.83	9.294%	$137.5246	$137.52	$137.50	$137.50
7 purchase totals =	$1,007.43		$1,099.6230	$1,099.62	$1,099.55	$1,099.50