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	$151.31	4.693%	$158.411	$158.41	$158.40	$158.40
Purchase #2	$216.58	4.611%	$226.5665	$226.57	$226.55	$226.60
Purchase #3	$105.84	7.769%	$114.0627	$114.06	$114.05	$114.10
Purchase #4	$167.40	13.850%	$190.5849	$190.58	$190.60	$190.60
Purchase #5	$14.77	5.163%	$15.5326	$15.53	$15.55	$15.50
Purchase #6	$218.26	13.284%	$247.2537	$247.25	$247.25	$247.30
Purchase #7	$81.70	9.632%	$89.5693	$89.57	$89.55	$89.60
7 purchase totals =	$955.86		$1,041.9807	$1,041.97	$1,041.95	$1,042.10