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	$48.75	4.806%	$51.0929	$51.09	$51.10	$51.10
Purchase #2	$223.98	5.169%	$235.5575	$235.56	$235.55	$235.60
Purchase #3	$42.72	13.635%	$48.5449	$48.54	$48.55	$48.50
Purchase #4	$226.25	12.521%	$254.5788	$254.58	$254.60	$254.60
Purchase #5	$135.54	3.579%	$140.391	$140.39	$140.40	$140.40
Purchase #6	$119.53	3.285%	$123.4566	$123.46	$123.45	$123.50
Purchase #7	$181.68	8.322%	$196.7994	$196.80	$196.80	$196.80
7 purchase totals =	$978.45		$1,050.4211	$1,050.42	$1,050.45	$1,050.50