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	$117.32	5.585%	$123.8723	$123.87	$123.85	$123.90
Purchase #2	$228.68	7.791%	$246.4965	$246.50	$246.50	$246.50
Purchase #3	$226.68	4.585%	$237.0733	$237.07	$237.05	$237.10
Purchase #4	$98.54	9.682%	$108.0806	$108.08	$108.10	$108.10
Purchase #5	$205.95	13.848%	$234.47	$234.47	$234.45	$234.50
Purchase #6	$33.98	10.250%	$37.463	$37.46	$37.45	$37.50
Purchase #7	$30.62	4.258%	$31.9238	$31.92	$31.90	$31.90
7 purchase totals =	$941.77		$1,019.3795	$1,019.37	$1,019.30	$1,019.50