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	$181.53	5.243%	$191.0476	$191.05	$191.05	$191.00
Purchase #2	$48.55	7.726%	$52.301	$52.30	$52.30	$52.30
Purchase #3	$121.60	9.222%	$132.814	$132.81	$132.80	$132.80
Purchase #4	$14.82	4.360%	$15.4662	$15.47	$15.45	$15.50
Purchase #5	$101.68	12.362%	$114.2497	$114.25	$114.25	$114.20
Purchase #6	$77.62	10.640%	$85.8788	$85.88	$85.90	$85.90
Purchase #7	$123.60	11.146%	$137.3765	$137.38	$137.40	$137.40
7 purchase totals =	$669.40		$729.1338	$729.14	$729.15	$729.10