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	$237.98	8.867%	$259.0817	$259.08	$259.10	$259.10
Purchase #2	$49.60	4.662%	$51.9124	$51.91	$51.90	$51.90
Purchase #3	$42.86	9.693%	$47.0144	$47.01	$47.00	$47.00
Purchase #4	$99.47	13.614%	$113.0118	$113.01	$113.00	$113.00
Purchase #5	$138.86	8.667%	$150.895	$150.90	$150.90	$150.90
Purchase #6	$233.83	7.240%	$250.7593	$250.76	$250.75	$250.80
Purchase #7	$133.72	5.792%	$141.4651	$141.47	$141.45	$141.50
7 purchase totals =	$936.32		$1,014.1397	$1,014.14	$1,014.10	$1,014.20