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	$131.49	12.774%	$148.2865	$148.29	$148.30	$148.30
Purchase #2	$142.26	11.434%	$158.526	$158.53	$158.55	$158.50
Purchase #3	$183.61	3.487%	$190.0125	$190.01	$190.00	$190.00
Purchase #4	$144.75	4.137%	$150.7383	$150.74	$150.75	$150.70
Purchase #5	$231.75	10.149%	$255.2703	$255.27	$255.25	$255.30
Purchase #6	$169.78	10.500%	$187.6069	$187.61	$187.60	$187.60
Purchase #7	$181.89	13.800%	$206.9908	$206.99	$207.00	$207.00
7 purchase totals =	$1,185.53		$1,297.4313	$1,297.44	$1,297.45	$1,297.40