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	$224.91	10.291%	$248.0555	$248.06	$248.05	$248.10
Purchase #2	$161.40	12.325%	$181.2926	$181.29	$181.30	$181.30
Purchase #3	$13.59	5.151%	$14.29	$14.29	$14.30	$14.30
Purchase #4	$106.43	6.195%	$113.0233	$113.02	$113.00	$113.00
Purchase #5	$18.42	6.308%	$19.5819	$19.58	$19.60	$19.60
Purchase #6	$26.48	11.353%	$29.4863	$29.49	$29.50	$29.50
Purchase #7	$59.63	3.290%	$61.5918	$61.59	$61.60	$61.60
7 purchase totals =	$610.86		$667.3214	$667.32	$667.35	$667.40