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	$104.38	9.720%	$114.5257	$114.53	$114.55	$114.50
Purchase #2	$18.29	3.436%	$18.9184	$18.92	$18.90	$18.90
Purchase #3	$183.54	3.663%	$190.2631	$190.26	$190.25	$190.30
Purchase #4	$95.83	3.834%	$99.5041	$99.50	$99.50	$99.50
Purchase #5	$176.43	6.712%	$188.272	$188.27	$188.25	$188.30
Purchase #6	$100.47	4.583%	$105.0745	$105.07	$105.05	$105.10
Purchase #7	$199.99	8.637%	$217.2631	$217.26	$217.25	$217.30
7 purchase totals =	$878.93		$933.8209	$933.81	$933.75	$933.90