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	$211.56	12.683%	$238.3922	$238.39	$238.40	$238.40
Purchase #2	$220.63	11.611%	$246.2473	$246.25	$246.25	$246.20
Purchase #3	$96.82	3.763%	$100.4633	$100.46	$100.45	$100.50
Purchase #4	$167.38	10.716%	$185.3164	$185.32	$185.30	$185.30
Purchase #5	$15.56	11.241%	$17.3091	$17.31	$17.30	$17.30
Purchase #6	$136.54	7.162%	$146.319	$146.32	$146.30	$146.30
Purchase #7	$175.87	13.321%	$199.2976	$199.30	$199.30	$199.30
7 purchase totals =	$1,024.36		$1,133.3449	$1,133.35	$1,133.30	$1,133.30