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	$68.84	9.337%	$75.2676	$75.27	$75.25	$75.30
Purchase #2	$127.80	13.863%	$145.5169	$145.52	$145.50	$145.50
Purchase #3	$182.90	5.301%	$192.5955	$192.60	$192.60	$192.60
Purchase #4	$196.32	7.195%	$210.4452	$210.45	$210.45	$210.40
Purchase #5	$95.53	10.416%	$105.4804	$105.48	$105.50	$105.50
Purchase #6	$222.90	7.793%	$240.2706	$240.27	$240.25	$240.30
Purchase #7	$44.82	6.454%	$47.7127	$47.71	$47.70	$47.70
7 purchase totals =	$939.11		$1,017.2889	$1,017.30	$1,017.25	$1,017.30