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	$161.79	5.431%	$170.5768	$170.58	$170.60	$170.60
Purchase #2	$123.51	13.866%	$140.6359	$140.64	$140.65	$140.60
Purchase #3	$224.89	5.325%	$236.8654	$236.87	$236.85	$236.90
Purchase #4	$31.85	4.123%	$33.1632	$33.16	$33.15	$33.20
Purchase #5	$171.82	4.408%	$179.3938	$179.39	$179.40	$179.40
Purchase #6	$168.72	7.408%	$181.2188	$181.22	$181.20	$181.20
Purchase #7	$33.67	7.586%	$36.2242	$36.22	$36.20	$36.20
7 purchase totals =	$916.25		$978.0781	$978.08	$978.05	$978.10