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	$59.65	3.291%	$61.6131	$61.61	$61.60	$61.60
Purchase #2	$105.27	10.783%	$116.6213	$116.62	$116.60	$116.60
Purchase #3	$107.87	10.543%	$119.2427	$119.24	$119.25	$119.20
Purchase #4	$242.48	11.188%	$269.6087	$269.61	$269.60	$269.60
Purchase #5	$197.53	12.560%	$222.3398	$222.34	$222.35	$222.30
Purchase #6	$66.82	8.269%	$72.3453	$72.35	$72.35	$72.30
Purchase #7	$121.77	4.264%	$126.9623	$126.96	$126.95	$127.00
7 purchase totals =	$901.39		$988.7332	$988.73	$988.70	$988.60