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	$68.93	13.721%	$78.3879	$78.39	$78.40	$78.40
Purchase #2	$19.38	9.794%	$21.2781	$21.28	$21.30	$21.30
Purchase #3	$30.87	12.360%	$34.6855	$34.69	$34.70	$34.70
Purchase #4	$144.42	12.236%	$162.0912	$162.09	$162.10	$162.10
Purchase #5	$237.45	11.606%	$265.0084	$265.01	$265.00	$265.00
Purchase #6	$147.57	3.710%	$153.0448	$153.04	$153.05	$153.00
Purchase #7	$105.89	3.596%	$109.6978	$109.70	$109.70	$109.70
7 purchase totals =	$754.51		$824.1937	$824.20	$824.25	$824.20