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	$245.65	5.530%	$259.2344	$259.23	$259.25	$259.20
Purchase #2	$18.59	13.268%	$21.0565	$21.06	$21.05	$21.10
Purchase #3	$245.41	3.630%	$254.3184	$254.32	$254.30	$254.30
Purchase #4	$173.51	7.125%	$185.8726	$185.87	$185.85	$185.90
Purchase #5	$151.32	3.607%	$156.7781	$156.78	$156.80	$156.80
Purchase #6	$74.71	4.343%	$77.9547	$77.95	$77.95	$78.00
Purchase #7	$117.44	11.193%	$130.5851	$130.59	$130.60	$130.60
7 purchase totals =	$1,026.63		$1,085.7998	$1,085.80	$1,085.80	$1,085.90