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	$76.65	12.726%	$86.4045	$86.40	$86.40	$86.40
Purchase #2	$82.91	8.243%	$89.7443	$89.74	$89.75	$89.70
Purchase #3	$82.28	9.484%	$90.0834	$90.08	$90.10	$90.10
Purchase #4	$218.87	10.222%	$241.2429	$241.24	$241.25	$241.20
Purchase #5	$191.60	9.156%	$209.1429	$209.14	$209.15	$209.10
Purchase #6	$97.42	8.401%	$105.6043	$105.60	$105.60	$105.60
Purchase #7	$218.42	9.145%	$238.3945	$238.39	$238.40	$238.40
7 purchase totals =	$968.15		$1,060.6168	$1,060.59	$1,060.65	$1,060.50