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	$123.83	3.326%	$127.9486	$127.95	$127.95	$127.90
Purchase #2	$131.32	11.679%	$146.6569	$146.66	$146.65	$146.70
Purchase #3	$151.75	3.147%	$156.5256	$156.53	$156.55	$156.50
Purchase #4	$136.71	8.848%	$148.8061	$148.81	$148.80	$148.80
Purchase #5	$73.59	6.829%	$78.6155	$78.62	$78.60	$78.60
Purchase #6	$101.77	10.790%	$112.751	$112.75	$112.75	$112.80
Purchase #7	$37.83	9.672%	$41.4889	$41.49	$41.50	$41.50
7 purchase totals =	$756.80		$812.7926	$812.81	$812.80	$812.80