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	$190.68	4.772%	$199.7792	$199.78	$199.80	$199.80
Purchase #2	$197.94	4.149%	$206.1525	$206.15	$206.15	$206.20
Purchase #3	$69.56	3.244%	$71.8165	$71.82	$71.80	$71.80
Purchase #4	$59.60	11.364%	$66.3729	$66.37	$66.35	$66.40
Purchase #5	$78.30	13.497%	$88.8682	$88.87	$88.85	$88.90
Purchase #6	$198.56	8.665%	$215.7652	$215.77	$215.75	$215.80
Purchase #7	$215.28	3.334%	$222.4574	$222.46	$222.45	$222.50
7 purchase totals =	$1,009.92		$1,071.2119	$1,071.22	$1,071.15	$1,071.40