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	$145.34	6.213%	$154.37	$154.37	$154.35	$154.40
Purchase #2	$156.64	7.413%	$168.2517	$168.25	$168.25	$168.30
Purchase #3	$157.83	5.500%	$166.5107	$166.51	$166.50	$166.50
Purchase #4	$184.27	3.516%	$190.7489	$190.75	$190.75	$190.70
Purchase #5	$215.40	13.835%	$245.2006	$245.20	$245.20	$245.20
Purchase #6	$46.53	9.859%	$51.1174	$51.12	$51.10	$51.10
Purchase #7	$178.28	7.390%	$191.4549	$191.45	$191.45	$191.50
7 purchase totals =	$1,084.29		$1,167.6542	$1,167.65	$1,167.60	$1,167.70