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	$25.42	13.449%	$28.8387	$28.84	$28.85	$28.80
Purchase #2	$158.72	6.509%	$169.0511	$169.05	$169.05	$169.10
Purchase #3	$215.99	6.236%	$229.4591	$229.46	$229.45	$229.50
Purchase #4	$242.46	8.243%	$262.446	$262.45	$262.45	$262.40
Purchase #5	$245.89	4.287%	$256.4313	$256.43	$256.45	$256.40
Purchase #6	$106.58	5.642%	$112.5932	$112.59	$112.60	$112.60
Purchase #7	$188.43	12.729%	$212.4153	$212.42	$212.40	$212.40
7 purchase totals =	$1,183.49		$1,271.2347	$1,271.24	$1,271.25	$1,271.20