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	$184.71	4.204%	$192.4752	$192.48	$192.50	$192.50
Purchase #2	$128.64	3.228%	$132.7925	$132.79	$132.80	$132.80
Purchase #3	$214.93	5.143%	$225.9838	$225.98	$226.00	$226.00
Purchase #4	$232.28	9.120%	$253.4639	$253.46	$253.45	$253.50
Purchase #5	$195.50	12.333%	$219.611	$219.61	$219.60	$219.60
Purchase #6	$136.45	5.870%	$144.4596	$144.46	$144.45	$144.50
Purchase #7	$135.55	3.157%	$139.8293	$139.83	$139.85	$139.80
7 purchase totals =	$1,228.06		$1,308.6153	$1,308.61	$1,308.65	$1,308.70