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	$182.87	8.492%	$198.3993	$198.40	$198.40	$198.40
Purchase #2	$52.84	12.368%	$59.3753	$59.38	$59.40	$59.40
Purchase #3	$61.37	6.289%	$65.2296	$65.23	$65.25	$65.20
Purchase #4	$47.99	5.269%	$50.5186	$50.52	$50.50	$50.50
Purchase #5	$123.94	6.706%	$132.2514	$132.25	$132.25	$132.30
Purchase #6	$120.83	9.384%	$132.1687	$132.17	$132.15	$132.20
Purchase #7	$41.95	13.870%	$47.7685	$47.77	$47.75	$47.80
7 purchase totals =	$631.79		$685.7114	$685.72	$685.70	$685.80