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	$149.41	3.421%	$154.5213	$154.52	$154.50	$154.50
Purchase #2	$112.41	5.403%	$118.4835	$118.48	$118.50	$118.50
Purchase #3	$100.81	10.215%	$111.1077	$111.11	$111.10	$111.10
Purchase #4	$7.37	5.680%	$7.7886	$7.79	$7.80	$7.80
Purchase #5	$97.51	12.751%	$109.9435	$109.94	$109.95	$109.90
Purchase #6	$39.54	12.262%	$44.3884	$44.39	$44.40	$44.40
Purchase #7	$204.94	10.773%	$227.0182	$227.02	$227.00	$227.00
7 purchase totals =	$711.99		$773.2512	$773.25	$773.25	$773.20