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	$97.70	10.524%	$107.9819	$107.98	$108.00	$108.00
Purchase #2	$79.46	3.785%	$82.4676	$82.47	$82.45	$82.50
Purchase #3	$117.81	4.845%	$123.5179	$123.52	$123.50	$123.50
Purchase #4	$156.99	10.122%	$172.8805	$172.88	$172.90	$172.90
Purchase #5	$82.60	10.636%	$91.3853	$91.39	$91.40	$91.40
Purchase #6	$186.90	3.653%	$193.7275	$193.73	$193.75	$193.70
Purchase #7	$249.65	11.565%	$278.522	$278.52	$278.50	$278.50
7 purchase totals =	$971.11		$1,050.4827	$1,050.49	$1,050.50	$1,050.50