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	$41.28	5.731%	$43.6458	$43.65	$43.65	$43.60
Purchase #2	$90.28	12.429%	$101.5009	$101.50	$101.50	$101.50
Purchase #3	$201.59	12.225%	$226.2344	$226.23	$226.25	$226.20
Purchase #4	$52.52	13.205%	$59.4553	$59.46	$59.45	$59.50
Purchase #5	$218.62	5.233%	$230.0604	$230.06	$230.05	$230.10
Purchase #6	$137.31	10.698%	$151.9994	$152.00	$152.00	$152.00
Purchase #7	$236.98	11.362%	$263.9057	$263.91	$263.90	$263.90
7 purchase totals =	$978.58		$1,076.8019	$1,076.81	$1,076.80	$1,076.80