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	$206.59	3.732%	$214.2999	$214.30	$214.30	$214.30
Purchase #2	$190.52	13.324%	$215.9049	$215.90	$215.90	$215.90
Purchase #3	$130.69	10.378%	$144.253	$144.25	$144.25	$144.30
Purchase #4	$91.90	11.430%	$102.4042	$102.40	$102.40	$102.40
Purchase #5	$222.77	7.433%	$239.3285	$239.33	$239.35	$239.30
Purchase #6	$130.30	12.549%	$146.6513	$146.65	$146.65	$146.70
Purchase #7	$98.89	10.854%	$109.6235	$109.62	$109.60	$109.60
7 purchase totals =	$1,071.66		$1,172.4653	$1,172.45	$1,172.45	$1,172.50