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	$224.98	3.677%	$233.2525	$233.25	$233.25	$233.30
Purchase #2	$33.72	13.609%	$38.309	$38.31	$38.30	$38.30
Purchase #3	$61.71	8.428%	$66.9109	$66.91	$66.90	$66.90
Purchase #4	$11.43	6.200%	$12.1387	$12.14	$12.15	$12.10
Purchase #5	$230.92	7.627%	$248.5323	$248.53	$248.55	$248.50
Purchase #6	$172.72	10.857%	$191.4722	$191.47	$191.45	$191.50
Purchase #7	$250.29	12.511%	$281.6038	$281.60	$281.60	$281.60
7 purchase totals =	$985.77		$1,072.2194	$1,072.21	$1,072.20	$1,072.20