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	$191.79	4.570%	$200.5548	$200.55	$200.55	$200.60
Purchase #2	$74.26	5.693%	$78.4876	$78.49	$78.50	$78.50
Purchase #3	$17.30	11.152%	$19.2293	$19.23	$19.25	$19.20
Purchase #4	$95.26	5.156%	$100.1716	$100.17	$100.15	$100.20
Purchase #5	$129.76	8.699%	$141.0478	$141.05	$141.05	$141.00
Purchase #6	$143.35	6.379%	$152.4943	$152.49	$152.50	$152.50
Purchase #7	$91.67	13.396%	$103.9501	$103.95	$103.95	$104.00
7 purchase totals =	$743.39		$795.9355	$795.93	$795.95	$796.00