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	$40.95	8.454%	$44.4119	$44.41	$44.40	$44.40
Purchase #2	$186.72	11.425%	$208.0528	$208.05	$208.05	$208.10
Purchase #3	$106.72	9.495%	$116.8531	$116.85	$116.85	$116.90
Purchase #4	$139.66	13.192%	$158.0839	$158.08	$158.10	$158.10
Purchase #5	$236.47	12.525%	$266.0879	$266.09	$266.10	$266.10
Purchase #6	$86.71	3.132%	$89.4258	$89.43	$89.45	$89.40
Purchase #7	$173.92	5.516%	$183.5134	$183.51	$183.50	$183.50
7 purchase totals =	$971.15		$1,066.4288	$1,066.42	$1,066.45	$1,066.50