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	$96.77	6.793%	$103.3436	$103.34	$103.35	$103.30
Purchase #2	$16.25	9.848%	$17.8503	$17.85	$17.85	$17.90
Purchase #3	$12.88	5.151%	$13.5434	$13.54	$13.55	$13.50
Purchase #4	$209.88	6.278%	$223.0563	$223.06	$223.05	$223.10
Purchase #5	$89.46	7.472%	$96.1445	$96.14	$96.15	$96.10
Purchase #6	$14.39	4.713%	$15.0682	$15.07	$15.05	$15.10
Purchase #7	$13.89	4.525%	$14.5185	$14.52	$14.50	$14.50
7 purchase totals =	$453.52		$483.5248	$483.52	$483.50	$483.50