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	$90.58	12.310%	$101.7304	$101.73	$101.75	$101.70
Purchase #2	$60.39	12.594%	$67.9955	$68.00	$68.00	$68.00
Purchase #3	$111.69	11.187%	$124.1848	$124.18	$124.20	$124.20
Purchase #4	$83.44	8.408%	$90.4556	$90.46	$90.45	$90.50
Purchase #5	$129.49	6.453%	$137.846	$137.85	$137.85	$137.80
Purchase #6	$147.32	6.227%	$156.4936	$156.49	$156.50	$156.50
Purchase #7	$72.90	6.233%	$77.4439	$77.44	$77.45	$77.40
7 purchase totals =	$695.81		$756.1498	$756.15	$756.20	$756.10