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	$121.53	9.342%	$132.8833	$132.88	$132.90	$132.90
Purchase #2	$250.95	13.723%	$285.3879	$285.39	$285.40	$285.40
Purchase #3	$112.45	11.104%	$124.9364	$124.94	$124.95	$124.90
Purchase #4	$92.76	13.522%	$105.303	$105.30	$105.30	$105.30
Purchase #5	$180.90	4.249%	$188.5864	$188.59	$188.60	$188.60
Purchase #6	$54.99	8.657%	$59.7505	$59.75	$59.75	$59.80
Purchase #7	$250.66	11.550%	$279.6112	$279.61	$279.60	$279.60
7 purchase totals =	$1,064.24		$1,176.4587	$1,176.46	$1,176.50	$1,176.50