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	$224.70	6.624%	$239.5841	$239.58	$239.60	$239.60
Purchase #2	$102.63	6.666%	$109.4713	$109.47	$109.45	$109.50
Purchase #3	$222.50	6.523%	$237.0137	$237.01	$237.00	$237.00
Purchase #4	$107.91	4.581%	$112.8534	$112.85	$112.85	$112.90
Purchase #5	$53.33	11.198%	$59.3019	$59.30	$59.30	$59.30
Purchase #6	$73.57	10.120%	$81.0153	$81.02	$81.00	$81.00
Purchase #7	$185.96	13.136%	$210.3877	$210.39	$210.40	$210.40
7 purchase totals =	$970.60		$1,049.6274	$1,049.62	$1,049.60	$1,049.70