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	$169.55	5.262%	$178.4717	$178.47	$178.45	$178.50
Purchase #2	$50.65	4.270%	$52.8128	$52.81	$52.80	$52.80
Purchase #3	$124.90	10.420%	$137.9146	$137.91	$137.90	$137.90
Purchase #4	$36.42	5.451%	$38.4053	$38.41	$38.40	$38.40
Purchase #5	$58.28	6.136%	$61.8561	$61.86	$61.85	$61.90
Purchase #6	$179.39	6.550%	$191.14	$191.14	$191.15	$191.10
Purchase #7	$148.26	9.203%	$161.9044	$161.90	$161.90	$161.90
7 purchase totals =	$767.45		$822.5049	$822.50	$822.45	$822.50