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	$177.86	4.278%	$185.4689	$185.47	$185.45	$185.50
Purchase #2	$142.59	9.754%	$156.4982	$156.50	$156.50	$156.50
Purchase #3	$7.27	11.222%	$8.0858	$8.09	$8.10	$8.10
Purchase #4	$203.56	7.823%	$219.4845	$219.48	$219.50	$219.50
Purchase #5	$190.56	3.102%	$196.4712	$196.47	$196.45	$196.50
Purchase #6	$106.89	13.623%	$121.4516	$121.45	$121.45	$121.50
Purchase #7	$130.93	11.502%	$145.9896	$145.99	$146.00	$146.00
7 purchase totals =	$959.66		$1,033.4498	$1,033.45	$1,033.45	$1,033.60