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	$116.70	5.824%	$123.4966	$123.50	$123.50	$123.50
Purchase #2	$218.65	10.401%	$241.3918	$241.39	$241.40	$241.40
Purchase #3	$63.71	4.242%	$66.4126	$66.41	$66.40	$66.40
Purchase #4	$186.93	7.485%	$200.9217	$200.92	$200.90	$200.90
Purchase #5	$181.98	5.555%	$192.089	$192.09	$192.10	$192.10
Purchase #6	$191.93	9.230%	$209.6451	$209.65	$209.65	$209.60
Purchase #7	$179.39	9.497%	$196.4267	$196.43	$196.45	$196.40
7 purchase totals =	$1,139.29		$1,230.3835	$1,230.39	$1,230.40	$1,230.30