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	$151.26	3.479%	$156.5223	$156.52	$156.50	$156.50
Purchase #2	$78.89	12.762%	$88.9579	$88.96	$88.95	$89.00
Purchase #3	$185.75	5.189%	$195.3886	$195.39	$195.40	$195.40
Purchase #4	$64.39	10.704%	$71.2823	$71.28	$71.30	$71.30
Purchase #5	$145.89	8.757%	$158.6656	$158.67	$158.65	$158.70
Purchase #6	$124.44	13.534%	$141.2817	$141.28	$141.30	$141.30
Purchase #7	$232.27	12.269%	$260.7672	$260.77	$260.75	$260.80
7 purchase totals =	$982.89		$1,072.8656	$1,072.87	$1,072.85	$1,073.00