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	$111.52	3.651%	$115.5916	$115.59	$115.60	$115.60
Purchase #2	$99.61	8.801%	$108.3767	$108.38	$108.40	$108.40
Purchase #3	$21.31	13.540%	$24.1954	$24.20	$24.20	$24.20
Purchase #4	$214.95	4.117%	$223.7995	$223.80	$223.80	$223.80
Purchase #5	$39.69	8.423%	$43.0331	$43.03	$43.05	$43.00
Purchase #6	$64.85	11.291%	$72.1722	$72.17	$72.15	$72.20
Purchase #7	$57.60	10.601%	$63.7062	$63.71	$63.70	$63.70
7 purchase totals =	$609.53		$650.8747	$650.88	$650.90	$650.90