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	$103.60	7.843%	$111.7253	$111.73	$111.75	$111.70
Purchase #2	$113.94	8.573%	$123.7081	$123.71	$123.70	$123.70
Purchase #3	$81.44	5.300%	$85.7563	$85.76	$85.75	$85.80
Purchase #4	$134.93	13.603%	$153.2845	$153.28	$153.30	$153.30
Purchase #5	$190.63	12.415%	$214.2967	$214.30	$214.30	$214.30
Purchase #6	$112.85	5.147%	$118.6584	$118.66	$118.65	$118.70
Purchase #7	$34.99	13.535%	$39.7259	$39.73	$39.75	$39.70
7 purchase totals =	$772.38		$847.1552	$847.17	$847.20	$847.20