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	$181.55	13.181%	$205.4801	$205.48	$205.50	$205.50
Purchase #2	$162.83	6.812%	$173.922	$173.92	$173.90	$173.90
Purchase #3	$54.76	5.760%	$57.9142	$57.91	$57.90	$57.90
Purchase #4	$89.56	11.743%	$100.077	$100.08	$100.10	$100.10
Purchase #5	$124.77	9.808%	$137.0074	$137.01	$137.00	$137.00
Purchase #6	$17.72	12.162%	$19.8751	$19.88	$19.90	$19.90
Purchase #7	$66.88	8.245%	$72.3943	$72.39	$72.40	$72.40
7 purchase totals =	$698.07		$766.6701	$766.67	$766.70	$766.70