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	$151.98	13.845%	$173.0216	$173.02	$173.00	$173.00
Purchase #2	$231.96	5.424%	$244.5415	$244.54	$244.55	$244.50
Purchase #3	$104.40	4.618%	$109.2212	$109.22	$109.20	$109.20
Purchase #4	$218.91	5.851%	$231.7184	$231.72	$231.70	$231.70
Purchase #5	$240.42	6.691%	$256.5065	$256.51	$256.50	$256.50
Purchase #6	$103.83	10.249%	$114.4715	$114.47	$114.45	$114.50
Purchase #7	$159.91	4.363%	$166.8869	$166.89	$166.90	$166.90
7 purchase totals =	$1,211.41		$1,296.3676	$1,296.37	$1,296.30	$1,296.30