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	$189.34	3.615%	$196.1846	$196.18	$196.20	$196.20
Purchase #2	$104.40	4.129%	$108.7107	$108.71	$108.70	$108.70
Purchase #3	$125.60	13.284%	$142.2847	$142.28	$142.30	$142.30
Purchase #4	$108.83	5.109%	$114.3901	$114.39	$114.40	$114.40
Purchase #5	$215.25	6.240%	$228.6816	$228.68	$228.70	$228.70
Purchase #6	$173.49	12.753%	$195.6152	$195.62	$195.60	$195.60
Purchase #7	$108.76	3.553%	$112.6242	$112.62	$112.60	$112.60
7 purchase totals =	$1,025.67		$1,098.4911	$1,098.48	$1,098.50	$1,098.50