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	$221.31	6.157%	$234.9361	$234.94	$234.95	$234.90
Purchase #2	$91.32	12.351%	$102.5989	$102.60	$102.60	$102.60
Purchase #3	$118.80	6.825%	$126.9081	$126.91	$126.90	$126.90
Purchase #4	$249.94	3.188%	$257.9081	$257.91	$257.90	$257.90
Purchase #5	$39.28	8.125%	$42.4715	$42.47	$42.45	$42.50
Purchase #6	$99.77	10.195%	$109.9416	$109.94	$109.95	$109.90
Purchase #7	$62.83	13.553%	$71.3453	$71.35	$71.35	$71.30
7 purchase totals =	$883.25		$946.1096	$946.12	$946.10	$946.00