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	$231.41	7.433%	$248.6107	$248.61	$248.60	$248.60
Purchase #2	$16.85	5.196%	$17.7255	$17.73	$17.75	$17.70
Purchase #3	$92.30	13.322%	$104.5962	$104.60	$104.60	$104.60
Purchase #4	$41.81	4.406%	$43.6521	$43.65	$43.65	$43.70
Purchase #5	$204.75	12.305%	$229.9445	$229.94	$229.95	$229.90
Purchase #6	$66.39	9.765%	$72.873	$72.87	$72.85	$72.90
Purchase #7	$221.85	3.429%	$229.4572	$229.46	$229.45	$229.50
7 purchase totals =	$875.36		$946.8592	$946.86	$946.85	$946.90