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	$119.54	6.383%	$127.1702	$127.17	$127.15	$127.20
Purchase #2	$70.76	13.558%	$80.3536	$80.35	$80.35	$80.40
Purchase #3	$127.65	4.271%	$133.1019	$133.10	$133.10	$133.10
Purchase #4	$19.39	5.458%	$20.4483	$20.45	$20.45	$20.40
Purchase #5	$157.55	10.475%	$174.0534	$174.05	$174.05	$174.10
Purchase #6	$74.28	7.218%	$79.6415	$79.64	$79.65	$79.60
Purchase #7	$141.84	6.699%	$151.3419	$151.34	$151.35	$151.30
7 purchase totals =	$711.01		$766.1108	$766.10	$766.10	$766.10