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	$212.50	9.793%	$233.3101	$233.31	$233.30	$233.30
Purchase #2	$18.77	5.315%	$19.7676	$19.77	$19.75	$19.80
Purchase #3	$70.75	11.275%	$78.7271	$78.73	$78.75	$78.70
Purchase #4	$161.36	10.665%	$178.569	$178.57	$178.55	$178.60
Purchase #5	$55.79	9.572%	$61.1302	$61.13	$61.15	$61.10
Purchase #6	$83.76	13.367%	$94.9562	$94.96	$94.95	$95.00
Purchase #7	$41.31	3.113%	$42.596	$42.60	$42.60	$42.60
7 purchase totals =	$644.24		$709.0562	$709.07	$709.05	$709.10