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	$227.68	13.576%	$258.5898	$258.59	$258.60	$258.60
Purchase #2	$8.91	13.490%	$10.112	$10.11	$10.10	$10.10
Purchase #3	$210.86	12.518%	$237.2555	$237.26	$237.25	$237.30
Purchase #4	$85.72	5.146%	$90.1312	$90.13	$90.15	$90.10
Purchase #5	$211.53	6.608%	$225.5079	$225.51	$225.50	$225.50
Purchase #6	$18.45	13.842%	$21.0038	$21.00	$21.00	$21.00
Purchase #7	$228.78	10.133%	$251.9623	$251.96	$251.95	$252.00
7 purchase totals =	$991.93		$1,094.5625	$1,094.56	$1,094.55	$1,094.60