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	$200.71	3.787%	$208.3109	$208.31	$208.30	$208.30
Purchase #2	$52.60	13.715%	$59.8141	$59.81	$59.80	$59.80
Purchase #3	$144.90	7.707%	$156.0674	$156.07	$156.05	$156.10
Purchase #4	$244.82	5.662%	$258.6817	$258.68	$258.70	$258.70
Purchase #5	$37.58	6.852%	$40.155	$40.16	$40.15	$40.20
Purchase #6	$47.59	10.419%	$52.5484	$52.55	$52.55	$52.50
Purchase #7	$96.28	6.772%	$102.8001	$102.80	$102.80	$102.80
7 purchase totals =	$824.48		$878.3776	$878.38	$878.35	$878.40