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	$225.38	12.333%	$253.1761	$253.18	$253.20	$253.20
Purchase #2	$222.95	9.845%	$244.8994	$244.90	$244.90	$244.90
Purchase #3	$39.35	3.823%	$40.8544	$40.85	$40.85	$40.90
Purchase #4	$212.77	10.364%	$234.8215	$234.82	$234.80	$234.80
Purchase #5	$12.89	6.153%	$13.6831	$13.68	$13.70	$13.70
Purchase #6	$87.30	13.704%	$99.2636	$99.26	$99.25	$99.30
Purchase #7	$246.93	4.170%	$257.227	$257.23	$257.25	$257.20
7 purchase totals =	$1,047.57		$1,143.9251	$1,143.92	$1,143.95	$1,144.00