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	$158.39	10.681%	$175.3076	$175.31	$175.30	$175.30
Purchase #2	$160.59	11.727%	$179.4224	$179.42	$179.40	$179.40
Purchase #3	$241.92	6.131%	$256.7521	$256.75	$256.75	$256.80
Purchase #4	$41.81	13.742%	$47.5555	$47.56	$47.55	$47.60
Purchase #5	$175.50	8.175%	$189.8471	$189.85	$189.85	$189.80
Purchase #6	$126.77	5.546%	$133.8007	$133.80	$133.80	$133.80
Purchase #7	$119.97	7.466%	$128.927	$128.93	$128.95	$128.90
7 purchase totals =	$1,024.95		$1,111.6124	$1,111.62	$1,111.60	$1,111.60