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	$59.65	9.276%	$65.1831	$65.18	$65.20	$65.20
Purchase #2	$69.79	12.634%	$78.6073	$78.61	$78.60	$78.60
Purchase #3	$170.86	12.455%	$192.1406	$192.14	$192.15	$192.10
Purchase #4	$119.79	7.496%	$128.7695	$128.77	$128.75	$128.80
Purchase #5	$220.59	4.459%	$230.4261	$230.43	$230.45	$230.40
Purchase #6	$129.36	6.111%	$137.2652	$137.27	$137.25	$137.30
Purchase #7	$178.52	7.308%	$191.5662	$191.57	$191.55	$191.60
7 purchase totals =	$948.56		$1,023.9580	$1,023.97	$1,023.95	$1,024.00