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	$232.52	3.445%	$240.5303	$240.53	$240.55	$240.50
Purchase #2	$190.53	3.184%	$196.5965	$196.60	$196.60	$196.60
Purchase #3	$69.51	13.707%	$79.0377	$79.04	$79.05	$79.00
Purchase #4	$73.84	9.421%	$80.7965	$80.80	$80.80	$80.80
Purchase #5	$154.72	7.129%	$165.75	$165.75	$165.75	$165.80
Purchase #6	$138.49	5.153%	$145.6264	$145.63	$145.65	$145.60
Purchase #7	$101.72	10.364%	$112.2623	$112.26	$112.25	$112.30
7 purchase totals =	$961.33		$1,020.5997	$1,020.61	$1,020.65	$1,020.60