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	$149.51	5.815%	$158.204	$158.20	$158.20	$158.20
Purchase #2	$47.59	8.312%	$51.5457	$51.55	$51.55	$51.50
Purchase #3	$131.43	12.469%	$147.818	$147.82	$147.80	$147.80
Purchase #4	$17.82	8.161%	$19.2743	$19.27	$19.25	$19.30
Purchase #5	$155.94	10.454%	$172.242	$172.24	$172.25	$172.20
Purchase #6	$148.46	8.368%	$160.8831	$160.88	$160.90	$160.90
Purchase #7	$75.52	3.610%	$78.2463	$78.25	$78.25	$78.20
7 purchase totals =	$726.27		$788.2134	$788.21	$788.20	$788.10