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	$223.53	5.477%	$235.7727	$235.77	$235.75	$235.80
Purchase #2	$137.86	4.716%	$144.3615	$144.36	$144.35	$144.40
Purchase #3	$42.72	3.236%	$44.1024	$44.10	$44.10	$44.10
Purchase #4	$115.54	7.298%	$123.9721	$123.97	$123.95	$124.00
Purchase #5	$160.60	12.340%	$180.418	$180.42	$180.40	$180.40
Purchase #6	$124.82	11.740%	$139.4739	$139.47	$139.45	$139.50
Purchase #7	$111.38	4.686%	$116.5993	$116.60	$116.60	$116.60
7 purchase totals =	$916.45		$984.6999	$984.69	$984.60	$984.80