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	$111.60	4.401%	$116.5115	$116.51	$116.50	$116.50
Purchase #2	$161.87	11.304%	$180.1678	$180.17	$180.15	$180.20
Purchase #3	$142.77	9.404%	$156.1961	$156.20	$156.20	$156.20
Purchase #4	$129.83	3.621%	$134.5311	$134.53	$134.55	$134.50
Purchase #5	$99.48	10.819%	$110.2427	$110.24	$110.25	$110.20
Purchase #6	$241.40	5.856%	$255.5364	$255.54	$255.55	$255.50
Purchase #7	$48.69	5.338%	$51.2891	$51.29	$51.30	$51.30
7 purchase totals =	$935.64		$1,004.4747	$1,004.48	$1,004.50	$1,004.40