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	$141.69	12.377%	$159.227	$159.23	$159.25	$159.20
Purchase #2	$74.58	4.445%	$77.8951	$77.90	$77.90	$77.90
Purchase #3	$144.49	6.827%	$154.3543	$154.35	$154.35	$154.40
Purchase #4	$183.83	7.331%	$197.3066	$197.31	$197.30	$197.30
Purchase #5	$146.34	13.540%	$166.1544	$166.15	$166.15	$166.20
Purchase #6	$73.46	9.733%	$80.6099	$80.61	$80.60	$80.60
Purchase #7	$133.90	6.778%	$142.9757	$142.98	$143.00	$143.00
7 purchase totals =	$898.29		$978.5230	$978.53	$978.55	$978.60