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	$144.91	8.656%	$157.4534	$157.45	$157.45	$157.50
Purchase #2	$238.43	10.522%	$263.5176	$263.52	$263.50	$263.50
Purchase #3	$106.67	4.188%	$111.1373	$111.14	$111.15	$111.10
Purchase #4	$179.48	5.134%	$188.6945	$188.69	$188.70	$188.70
Purchase #5	$146.90	7.255%	$157.5576	$157.56	$157.55	$157.60
Purchase #6	$13.90	4.464%	$14.5205	$14.52	$14.50	$14.50
Purchase #7	$151.40	4.502%	$158.216	$158.22	$158.20	$158.20
7 purchase totals =	$981.69		$1,051.0969	$1,051.10	$1,051.05	$1,051.10