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	$118.29	7.363%	$126.9997	$127.00	$127.00	$127.00
Purchase #2	$105.40	12.313%	$118.3779	$118.38	$118.40	$118.40
Purchase #3	$131.26	10.130%	$144.5566	$144.56	$144.55	$144.60
Purchase #4	$145.69	7.602%	$156.7654	$156.77	$156.75	$156.80
Purchase #5	$235.31	10.648%	$260.3658	$260.37	$260.35	$260.40
Purchase #6	$46.55	13.765%	$52.9576	$52.96	$52.95	$53.00
Purchase #7	$14.89	3.149%	$15.3589	$15.36	$15.35	$15.40
7 purchase totals =	$797.39		$875.3819	$875.40	$875.35	$875.60