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	$114.60	8.111%	$123.8952	$123.90	$123.90	$123.90
Purchase #2	$241.71	4.149%	$251.7385	$251.74	$251.75	$251.70
Purchase #3	$97.26	3.350%	$100.5182	$100.52	$100.50	$100.50
Purchase #4	$131.72	4.562%	$137.7291	$137.73	$137.75	$137.70
Purchase #5	$52.26	5.243%	$55	$55.00	$55.00	$55.00
Purchase #6	$43.69	11.472%	$48.7021	$48.70	$48.70	$48.70
Purchase #7	$93.95	11.561%	$104.8116	$104.81	$104.80	$104.80
7 purchase totals =	$775.19		$822.3947	$822.40	$822.40	$822.30