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	$219.79	13.694%	$249.888	$249.89	$249.90	$249.90
Purchase #2	$49.44	6.258%	$52.534	$52.53	$52.55	$52.50
Purchase #3	$207.93	9.611%	$227.9142	$227.91	$227.90	$227.90
Purchase #4	$54.73	12.388%	$61.51	$61.51	$61.50	$61.50
Purchase #5	$236.79	6.201%	$251.4733	$251.47	$251.45	$251.50
Purchase #6	$127.71	11.137%	$141.9331	$141.93	$141.95	$141.90
Purchase #7	$47.52	9.803%	$52.1784	$52.18	$52.20	$52.20
7 purchase totals =	$943.91		$1,037.4310	$1,037.42	$1,037.45	$1,037.40