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	$97.41	8.447%	$105.6382	$105.64	$105.65	$105.60
Purchase #2	$23.49	4.669%	$24.5867	$24.59	$24.60	$24.60
Purchase #3	$18.82	13.327%	$21.3281	$21.33	$21.35	$21.30
Purchase #4	$250.82	13.688%	$285.1522	$285.15	$285.15	$285.20
Purchase #5	$135.59	12.191%	$152.1198	$152.12	$152.10	$152.10
Purchase #6	$220.68	9.406%	$241.4372	$241.44	$241.45	$241.40
Purchase #7	$38.39	4.251%	$40.022	$40.02	$40.00	$40.00
7 purchase totals =	$785.20		$870.2842	$870.29	$870.30	$870.20