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	$146.56	4.747%	$153.5172	$153.52	$153.50	$153.50
Purchase #2	$48.62	4.477%	$50.7967	$50.80	$50.80	$50.80
Purchase #3	$135.49	5.732%	$143.2563	$143.26	$143.25	$143.30
Purchase #4	$100.96	10.816%	$111.8798	$111.88	$111.90	$111.90
Purchase #5	$62.50	5.261%	$65.7881	$65.79	$65.80	$65.80
Purchase #6	$75.37	9.637%	$82.6334	$82.63	$82.65	$82.60
Purchase #7	$216.84	4.396%	$226.3723	$226.37	$226.35	$226.40
7 purchase totals =	$786.34		$834.2438	$834.25	$834.25	$834.30