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	$225.72	9.790%	$247.818	$247.82	$247.80	$247.80
Purchase #2	$97.47	8.650%	$105.9012	$105.90	$105.90	$105.90
Purchase #3	$200.43	12.664%	$225.8125	$225.81	$225.80	$225.80
Purchase #4	$149.42	13.826%	$170.0788	$170.08	$170.10	$170.10
Purchase #5	$159.54	10.296%	$175.9662	$175.97	$175.95	$176.00
Purchase #6	$78.38	13.711%	$89.1267	$89.13	$89.15	$89.10
Purchase #7	$37.29	5.790%	$39.4491	$39.45	$39.45	$39.40
7 purchase totals =	$948.25		$1,054.1525	$1,054.16	$1,054.15	$1,054.10