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	$75.71	10.383%	$83.571	$83.57	$83.55	$83.60
Purchase #2	$50.94	6.611%	$54.3076	$54.31	$54.30	$54.30
Purchase #3	$115.63	10.671%	$127.9689	$127.97	$127.95	$128.00
Purchase #4	$30.52	6.115%	$32.3863	$32.39	$32.40	$32.40
Purchase #5	$133.64	9.219%	$145.9603	$145.96	$145.95	$146.00
Purchase #6	$128.75	12.612%	$144.988	$144.99	$145.00	$145.00
Purchase #7	$96.91	9.142%	$105.7695	$105.77	$105.75	$105.80
7 purchase totals =	$632.10		$694.9516	$694.96	$694.90	$695.10