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	$238.83	5.843%	$252.7848	$252.78	$252.80	$252.80
Purchase #2	$150.88	10.319%	$166.4493	$166.45	$166.45	$166.40
Purchase #3	$222.29	8.555%	$241.3069	$241.31	$241.30	$241.30
Purchase #4	$90.43	9.261%	$98.8047	$98.80	$98.80	$98.80
Purchase #5	$127.56	10.382%	$140.8033	$140.80	$140.80	$140.80
Purchase #6	$85.87	3.435%	$88.8196	$88.82	$88.80	$88.80
Purchase #7	$32.60	11.208%	$36.2538	$36.25	$36.25	$36.30
7 purchase totals =	$948.46		$1,025.2224	$1,025.21	$1,025.20	$1,025.20