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	$189.78	3.772%	$196.9385	$196.94	$196.95	$196.90
Purchase #2	$105.25	11.536%	$117.3916	$117.39	$117.40	$117.40
Purchase #3	$127.80	9.492%	$139.9308	$139.93	$139.95	$139.90
Purchase #4	$125.59	8.651%	$136.4548	$136.45	$136.45	$136.50
Purchase #5	$88.86	6.475%	$94.6137	$94.61	$94.60	$94.60
Purchase #6	$206.87	5.648%	$218.554	$218.55	$218.55	$218.60
Purchase #7	$70.31	12.725%	$79.2569	$79.26	$79.25	$79.30
7 purchase totals =	$914.46		$983.1403	$983.13	$983.15	$983.20