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	$47.95	12.769%	$54.0727	$54.07	$54.05	$54.10
Purchase #2	$93.43	12.818%	$105.4059	$105.41	$105.40	$105.40
Purchase #3	$182.51	3.871%	$189.575	$189.58	$189.60	$189.60
Purchase #4	$146.53	10.243%	$161.5391	$161.54	$161.55	$161.50
Purchase #5	$24.39	11.748%	$27.2553	$27.26	$27.25	$27.30
Purchase #6	$204.63	11.675%	$228.5206	$228.52	$228.50	$228.50
Purchase #7	$77.96	5.720%	$82.4193	$82.42	$82.40	$82.40
7 purchase totals =	$777.40		$848.7879	$848.80	$848.75	$848.80