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	$215.51	13.350%	$244.2806	$244.28	$244.30	$244.30
Purchase #2	$86.55	13.139%	$97.9218	$97.92	$97.90	$97.90
Purchase #3	$181.53	6.102%	$192.607	$192.61	$192.60	$192.60
Purchase #4	$230.88	12.491%	$259.7192	$259.72	$259.70	$259.70
Purchase #5	$150.35	10.263%	$165.7804	$165.78	$165.80	$165.80
Purchase #6	$128.97	9.683%	$141.4582	$141.46	$141.45	$141.50
Purchase #7	$115.37	10.314%	$127.2693	$127.27	$127.25	$127.30
7 purchase totals =	$1,109.16		$1,229.0365	$1,229.04	$1,229.00	$1,229.10