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	$215.35	11.834%	$240.8345	$240.83	$240.85	$240.80
Purchase #2	$76.56	13.841%	$87.1567	$87.16	$87.15	$87.20
Purchase #3	$49.48	8.144%	$53.5097	$53.51	$53.50	$53.50
Purchase #4	$189.85	13.331%	$215.1589	$215.16	$215.15	$215.20
Purchase #5	$112.99	6.628%	$120.479	$120.48	$120.50	$120.50
Purchase #6	$114.83	10.646%	$127.0548	$127.05	$127.05	$127.10
Purchase #7	$232.63	9.736%	$255.2789	$255.28	$255.30	$255.30
7 purchase totals =	$991.69		$1,099.4725	$1,099.47	$1,099.50	$1,099.60