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	$211.33	7.606%	$227.4038	$227.40	$227.40	$227.40
Purchase #2	$241.28	4.457%	$252.0338	$252.03	$252.05	$252.00
Purchase #3	$209.72	10.291%	$231.3023	$231.30	$231.30	$231.30
Purchase #4	$10.82	9.633%	$11.8623	$11.86	$11.85	$11.90
Purchase #5	$176.65	12.793%	$199.2488	$199.25	$199.25	$199.20
Purchase #6	$85.89	5.346%	$90.4817	$90.48	$90.50	$90.50
Purchase #7	$153.79	4.506%	$160.7198	$160.72	$160.70	$160.70
7 purchase totals =	$1,089.48		$1,173.0525	$1,173.04	$1,173.05	$1,173.00