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	$117.59	5.753%	$124.355	$124.36	$124.35	$124.40
Purchase #2	$114.41	8.193%	$123.7836	$123.78	$123.80	$123.80
Purchase #3	$205.38	12.145%	$230.3234	$230.32	$230.30	$230.30
Purchase #4	$205.47	13.533%	$233.2763	$233.28	$233.30	$233.30
Purchase #5	$14.50	5.803%	$15.3414	$15.34	$15.35	$15.30
Purchase #6	$216.45	3.517%	$224.0625	$224.06	$224.05	$224.10
Purchase #7	$98.51	13.788%	$112.0926	$112.09	$112.10	$112.10
7 purchase totals =	$972.31		$1,063.2348	$1,063.23	$1,063.25	$1,063.30