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	$52.56	10.166%	$57.9032	$57.90	$57.90	$57.90
Purchase #2	$105.67	13.230%	$119.6501	$119.65	$119.65	$119.70
Purchase #3	$185.38	5.694%	$195.9355	$195.94	$195.95	$195.90
Purchase #4	$23.59	9.654%	$25.8674	$25.87	$25.85	$25.90
Purchase #5	$72.39	4.187%	$75.421	$75.42	$75.40	$75.40
Purchase #6	$151.75	13.671%	$172.4957	$172.50	$172.50	$172.50
Purchase #7	$98.70	6.503%	$105.1185	$105.12	$105.10	$105.10
7 purchase totals =	$690.04		$752.3914	$752.40	$752.35	$752.40