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	$160.28	10.172%	$176.5837	$176.58	$176.60	$176.60
Purchase #2	$28.87	12.370%	$32.4412	$32.44	$32.45	$32.40
Purchase #3	$188.86	13.484%	$214.3259	$214.33	$214.35	$214.30
Purchase #4	$48.86	11.612%	$54.5336	$54.53	$54.55	$54.50
Purchase #5	$196.67	11.687%	$219.6548	$219.65	$219.65	$219.70
Purchase #6	$135.77	7.411%	$145.8319	$145.83	$145.85	$145.80
Purchase #7	$239.25	12.830%	$269.9458	$269.95	$269.95	$269.90
7 purchase totals =	$998.56		$1,113.3169	$1,113.31	$1,113.40	$1,113.20