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	$126.60	3.305%	$130.7841	$130.78	$130.80	$130.80
Purchase #2	$209.49	11.523%	$233.6295	$233.63	$233.65	$233.60
Purchase #3	$215.81	10.684%	$238.8671	$238.87	$238.85	$238.90
Purchase #4	$53.76	10.297%	$59.2957	$59.30	$59.30	$59.30
Purchase #5	$248.91	9.320%	$272.1084	$272.11	$272.10	$272.10
Purchase #6	$41.50	13.333%	$47.0332	$47.03	$47.05	$47.00
Purchase #7	$215.55	3.196%	$222.439	$222.44	$222.45	$222.40
7 purchase totals =	$1,111.62		$1,204.1570	$1,204.16	$1,204.20	$1,204.10