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	$74.57	13.607%	$84.7167	$84.72	$84.70	$84.70
Purchase #2	$51.57	4.398%	$53.838	$53.84	$53.85	$53.80
Purchase #3	$161.73	6.698%	$172.5627	$172.56	$172.55	$172.60
Purchase #4	$116.80	5.810%	$123.5861	$123.59	$123.60	$123.60
Purchase #5	$9.98	7.831%	$10.7615	$10.76	$10.75	$10.80
Purchase #6	$204.96	10.183%	$225.8311	$225.83	$225.85	$225.80
Purchase #7	$117.99	5.705%	$124.7213	$124.72	$124.70	$124.70
7 purchase totals =	$737.60		$796.0174	$796.02	$796.00	$796.00