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	$95.79	9.476%	$104.8671	$104.87	$104.85	$104.90
Purchase #2	$123.47	12.827%	$139.3075	$139.31	$139.30	$139.30
Purchase #3	$17.91	5.593%	$18.9117	$18.91	$18.90	$18.90
Purchase #4	$218.82	12.161%	$245.4307	$245.43	$245.45	$245.40
Purchase #5	$57.83	8.650%	$62.8323	$62.83	$62.85	$62.80
Purchase #6	$37.56	5.278%	$39.5424	$39.54	$39.55	$39.50
Purchase #7	$131.45	11.114%	$146.0594	$146.06	$146.05	$146.10
7 purchase totals =	$682.83		$756.9511	$756.95	$756.95	$756.90