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	$245.52	13.317%	$278.2159	$278.22	$278.20	$278.20
Purchase #2	$214.93	5.446%	$226.6351	$226.64	$226.65	$226.60
Purchase #3	$48.86	13.483%	$55.4478	$55.45	$55.45	$55.40
Purchase #4	$140.72	5.585%	$148.5792	$148.58	$148.60	$148.60
Purchase #5	$80.86	3.157%	$83.4128	$83.41	$83.40	$83.40
Purchase #6	$148.89	12.690%	$167.7841	$167.78	$167.80	$167.80
Purchase #7	$125.68	6.860%	$134.3016	$134.30	$134.30	$134.30
7 purchase totals =	$1,005.46		$1,094.3765	$1,094.38	$1,094.40	$1,094.30