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	$227.51	11.602%	$253.9057	$253.91	$253.90	$253.90
Purchase #2	$55.50	7.134%	$59.4594	$59.46	$59.45	$59.50
Purchase #3	$81.64	10.828%	$90.48	$90.48	$90.50	$90.50
Purchase #4	$204.84	6.326%	$217.7982	$217.80	$217.80	$217.80
Purchase #5	$33.99	7.498%	$36.5386	$36.54	$36.55	$36.50
Purchase #6	$188.77	13.514%	$214.2804	$214.28	$214.30	$214.30
Purchase #7	$81.48	13.380%	$92.382	$92.38	$92.40	$92.40
7 purchase totals =	$873.73		$964.8443	$964.85	$964.90	$964.90