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	$176.34	6.688%	$188.1336	$188.13	$188.15	$188.10
Purchase #2	$102.39	8.856%	$111.4577	$111.46	$111.45	$111.50
Purchase #3	$67.73	4.371%	$70.6905	$70.69	$70.70	$70.70
Purchase #4	$232.56	12.683%	$262.0556	$262.06	$262.05	$262.10
Purchase #5	$178.34	6.710%	$190.3066	$190.31	$190.30	$190.30
Purchase #6	$119.92	7.172%	$128.5207	$128.52	$128.50	$128.50
Purchase #7	$182.26	8.351%	$197.4805	$197.48	$197.50	$197.50
7 purchase totals =	$1,059.54		$1,148.6452	$1,148.65	$1,148.65	$1,148.70