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	$144.45	4.464%	$150.8982	$150.90	$150.90	$150.90
Purchase #2	$28.51	4.737%	$29.8605	$29.86	$29.85	$29.90
Purchase #3	$29.86	12.234%	$33.5131	$33.51	$33.50	$33.50
Purchase #4	$178.51	8.729%	$194.0921	$194.09	$194.10	$194.10
Purchase #5	$133.32	6.629%	$142.1578	$142.16	$142.15	$142.20
Purchase #6	$46.50	4.755%	$48.7111	$48.71	$48.70	$48.70
Purchase #7	$15.52	4.680%	$16.2463	$16.25	$16.25	$16.20
7 purchase totals =	$576.67		$615.4791	$615.48	$615.45	$615.50