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	$49.32	4.692%	$51.6341	$51.63	$51.65	$51.60
Purchase #2	$227.72	7.407%	$244.5872	$244.59	$244.60	$244.60
Purchase #3	$220.89	6.133%	$234.4372	$234.44	$234.45	$234.40
Purchase #4	$172.51	7.151%	$184.8462	$184.85	$184.85	$184.80
Purchase #5	$159.67	9.671%	$175.1117	$175.11	$175.10	$175.10
Purchase #6	$38.87	11.593%	$43.3762	$43.38	$43.40	$43.40
Purchase #7	$59.83	13.833%	$68.1063	$68.11	$68.10	$68.10
7 purchase totals =	$928.81		$1,002.0989	$1,002.11	$1,002.15	$1,002.00