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	$176.53	4.618%	$184.6822	$184.68	$184.70	$184.70
Purchase #2	$31.66	6.671%	$33.772	$33.77	$33.75	$33.80
Purchase #3	$62.50	11.693%	$69.8081	$69.81	$69.80	$69.80
Purchase #4	$102.52	13.415%	$116.2731	$116.27	$116.25	$116.30
Purchase #5	$179.65	3.281%	$185.5443	$185.54	$185.55	$185.50
Purchase #6	$55.72	12.332%	$62.5914	$62.59	$62.60	$62.60
Purchase #7	$199.72	3.431%	$206.5724	$206.57	$206.55	$206.60
7 purchase totals =	$808.30		$859.2435	$859.23	$859.20	$859.30