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	$221.43	4.810%	$232.0808	$232.08	$232.10	$232.10
Purchase #2	$128.76	3.475%	$133.2344	$133.23	$133.25	$133.20
Purchase #3	$37.50	13.262%	$42.4733	$42.47	$42.45	$42.50
Purchase #4	$66.78	11.353%	$74.3615	$74.36	$74.35	$74.40
Purchase #5	$77.33	13.713%	$87.9343	$87.93	$87.95	$87.90
Purchase #6	$54.77	13.760%	$62.3064	$62.31	$62.30	$62.30
Purchase #7	$36.89	12.407%	$41.4669	$41.47	$41.45	$41.50
7 purchase totals =	$623.46		$673.8576	$673.85	$673.85	$673.90