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	$136.33	3.848%	$141.576	$141.58	$141.60	$141.60
Purchase #2	$122.75	6.522%	$130.7558	$130.76	$130.75	$130.80
Purchase #3	$228.33	11.390%	$254.3368	$254.34	$254.35	$254.30
Purchase #4	$129.57	12.386%	$145.6185	$145.62	$145.60	$145.60
Purchase #5	$119.51	6.530%	$127.314	$127.31	$127.30	$127.30
Purchase #6	$222.62	6.286%	$236.6139	$236.61	$236.60	$236.60
Purchase #7	$56.90	7.362%	$61.089	$61.09	$61.10	$61.10
7 purchase totals =	$1,016.01		$1,097.3040	$1,097.31	$1,097.30	$1,097.30