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	$227.60	4.650%	$238.1834	$238.18	$238.20	$238.20
Purchase #2	$137.82	10.444%	$152.2139	$152.21	$152.20	$152.20
Purchase #3	$104.83	6.777%	$111.9343	$111.93	$111.95	$111.90
Purchase #4	$94.54	9.623%	$103.6376	$103.64	$103.65	$103.60
Purchase #5	$159.47	10.523%	$176.251	$176.25	$176.25	$176.30
Purchase #6	$225.77	8.536%	$245.0417	$245.04	$245.05	$245.00
Purchase #7	$106.78	11.394%	$118.9465	$118.95	$118.95	$118.90
7 purchase totals =	$1,056.81		$1,146.2084	$1,146.20	$1,146.25	$1,146.10