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	$51.82	3.786%	$53.7819	$53.78	$53.80	$53.80
Purchase #2	$92.51	13.710%	$105.1931	$105.19	$105.20	$105.20
Purchase #3	$191.69	11.457%	$213.6519	$213.65	$213.65	$213.70
Purchase #4	$113.83	4.196%	$118.6063	$118.61	$118.60	$118.60
Purchase #5	$113.65	9.187%	$124.091	$124.09	$124.10	$124.10
Purchase #6	$216.80	4.725%	$227.0438	$227.04	$227.05	$227.00
Purchase #7	$53.97	12.132%	$60.5176	$60.52	$60.50	$60.50
7 purchase totals =	$834.27		$902.8856	$902.88	$902.90	$902.90