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	$182.85	4.591%	$191.2446	$191.24	$191.25	$191.20
Purchase #2	$124.85	9.761%	$137.0366	$137.04	$137.05	$137.00
Purchase #3	$34.54	4.632%	$36.1399	$36.14	$36.15	$36.10
Purchase #4	$56.90	8.338%	$61.6443	$61.64	$61.65	$61.60
Purchase #5	$146.29	3.325%	$151.1541	$151.15	$151.15	$151.20
Purchase #6	$18.79	13.843%	$21.3911	$21.39	$21.40	$21.40
Purchase #7	$126.54	4.744%	$132.5431	$132.54	$132.55	$132.50
7 purchase totals =	$690.76		$731.1537	$731.14	$731.20	$731.00