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	$211.62	8.684%	$229.9971	$230.00	$230.00	$230.00
Purchase #2	$27.85	9.143%	$30.3963	$30.40	$30.40	$30.40
Purchase #3	$23.72	8.391%	$25.7103	$25.71	$25.70	$25.70
Purchase #4	$64.31	13.154%	$72.7693	$72.77	$72.75	$72.80
Purchase #5	$42.80	3.511%	$44.3027	$44.30	$44.30	$44.30
Purchase #6	$78.45	9.250%	$85.7066	$85.71	$85.70	$85.70
Purchase #7	$123.41	3.322%	$127.5097	$127.51	$127.50	$127.50
7 purchase totals =	$572.16		$616.3920	$616.40	$616.35	$616.40