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	$193.52	3.816%	$200.9047	$200.90	$200.90	$200.90
Purchase #2	$80.73	11.441%	$89.9663	$89.97	$89.95	$90.00
Purchase #3	$136.50	7.135%	$146.2393	$146.24	$146.25	$146.20
Purchase #4	$83.64	8.180%	$90.4818	$90.48	$90.50	$90.50
Purchase #5	$53.48	5.151%	$56.2348	$56.23	$56.25	$56.20
Purchase #6	$132.78	13.385%	$150.5526	$150.55	$150.55	$150.60
Purchase #7	$38.51	4.230%	$40.139	$40.14	$40.15	$40.10
7 purchase totals =	$719.16		$774.5185	$774.51	$774.55	$774.50