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	$141.66	7.193%	$151.8496	$151.85	$151.85	$151.80
Purchase #2	$136.93	13.152%	$154.939	$154.94	$154.95	$154.90
Purchase #3	$139.71	3.778%	$144.9882	$144.99	$145.00	$145.00
Purchase #4	$95.61	10.231%	$105.3919	$105.39	$105.40	$105.40
Purchase #5	$19.87	6.225%	$21.1069	$21.11	$21.10	$21.10
Purchase #6	$118.40	10.648%	$131.0072	$131.01	$131.00	$131.00
Purchase #7	$117.53	8.338%	$127.3297	$127.33	$127.35	$127.30
7 purchase totals =	$769.71		$836.6125	$836.62	$836.65	$836.50