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	$219.48	7.750%	$236.4897	$236.49	$236.50	$236.50
Purchase #2	$106.78	4.478%	$111.5616	$111.56	$111.55	$111.60
Purchase #3	$173.66	10.679%	$192.2052	$192.21	$192.20	$192.20
Purchase #4	$44.85	6.671%	$47.8419	$47.84	$47.85	$47.80
Purchase #5	$100.59	9.151%	$109.795	$109.80	$109.80	$109.80
Purchase #6	$94.48	10.700%	$104.5894	$104.59	$104.60	$104.60
Purchase #7	$119.68	11.799%	$133.801	$133.80	$133.80	$133.80
7 purchase totals =	$859.52		$936.2838	$936.29	$936.30	$936.30