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	$209.84	5.147%	$220.6405	$220.64	$220.65	$220.60
Purchase #2	$10.75	5.751%	$11.3682	$11.37	$11.35	$11.40
Purchase #3	$72.85	7.291%	$78.1615	$78.16	$78.15	$78.20
Purchase #4	$188.39	10.684%	$208.5176	$208.52	$208.50	$208.50
Purchase #5	$40.64	6.229%	$43.1715	$43.17	$43.15	$43.20
Purchase #6	$121.64	7.835%	$131.1705	$131.17	$131.15	$131.20
Purchase #7	$40.88	11.450%	$45.5608	$45.56	$45.55	$45.60
7 purchase totals =	$684.99		$738.5906	$738.59	$738.50	$738.70