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	$228.68	10.870%	$253.5375	$253.54	$253.55	$253.50
Purchase #2	$140.38	8.501%	$152.3137	$152.31	$152.30	$152.30
Purchase #3	$249.49	3.568%	$258.3918	$258.39	$258.40	$258.40
Purchase #4	$129.98	12.731%	$146.5278	$146.53	$146.55	$146.50
Purchase #5	$164.64	5.291%	$173.3511	$173.35	$173.35	$173.40
Purchase #6	$160.44	7.167%	$171.9387	$171.94	$171.95	$171.90
Purchase #7	$52.27	4.678%	$54.7152	$54.72	$54.70	$54.70
7 purchase totals =	$1,125.88		$1,210.7758	$1,210.78	$1,210.80	$1,210.70