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	$82.41	4.523%	$86.1374	$86.14	$86.15	$86.10
Purchase #2	$129.29	4.283%	$134.8275	$134.83	$134.85	$134.80
Purchase #3	$51.40	11.247%	$57.181	$57.18	$57.20	$57.20
Purchase #4	$190.94	10.670%	$211.3133	$211.31	$211.30	$211.30
Purchase #5	$164.67	8.165%	$178.1153	$178.12	$178.10	$178.10
Purchase #6	$105.49	5.570%	$111.3658	$111.37	$111.35	$111.40
Purchase #7	$102.70	12.429%	$115.4646	$115.46	$115.45	$115.50
7 purchase totals =	$826.90		$894.4049	$894.41	$894.40	$894.40