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	$238.61	9.279%	$260.7506	$260.75	$260.75	$260.80
Purchase #2	$38.89	8.683%	$42.2668	$42.27	$42.25	$42.30
Purchase #3	$134.85	6.496%	$143.6099	$143.61	$143.60	$143.60
Purchase #4	$48.28	8.526%	$52.3964	$52.40	$52.40	$52.40
Purchase #5	$198.78	12.821%	$224.2656	$224.27	$224.25	$224.30
Purchase #6	$94.71	4.698%	$99.1595	$99.16	$99.15	$99.20
Purchase #7	$232.33	6.710%	$247.9193	$247.92	$247.90	$247.90
7 purchase totals =	$986.45		$1,070.3681	$1,070.38	$1,070.30	$1,070.50