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	$72.81	7.513%	$78.2802	$78.28	$78.30	$78.30
Purchase #2	$12.32	13.409%	$13.972	$13.97	$13.95	$14.00
Purchase #3	$68.46	4.505%	$71.5441	$71.54	$71.55	$71.50
Purchase #4	$220.40	3.558%	$228.2418	$228.24	$228.25	$228.20
Purchase #5	$225.33	13.182%	$255.033	$255.03	$255.05	$255.00
Purchase #6	$63.30	11.228%	$70.4073	$70.41	$70.40	$70.40
Purchase #7	$52.69	10.241%	$58.086	$58.09	$58.10	$58.10
7 purchase totals =	$715.31		$775.5644	$775.56	$775.60	$775.50