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	$89.48	7.197%	$95.9199	$95.92	$95.90	$95.90
Purchase #2	$157.79	3.734%	$163.6819	$163.68	$163.70	$163.70
Purchase #3	$118.43	7.491%	$127.3016	$127.30	$127.30	$127.30
Purchase #4	$175.60	7.601%	$188.9474	$188.95	$188.95	$188.90
Purchase #5	$104.44	5.218%	$109.8897	$109.89	$109.90	$109.90
Purchase #6	$77.42	6.122%	$82.1597	$82.16	$82.15	$82.20
Purchase #7	$49.30	13.431%	$55.9215	$55.92	$55.90	$55.90
7 purchase totals =	$772.46		$823.8217	$823.82	$823.80	$823.80