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	$247.68	11.361%	$275.8189	$275.82	$275.80	$275.80
Purchase #2	$131.66	12.868%	$148.602	$148.60	$148.60	$148.60
Purchase #3	$97.68	9.156%	$106.6236	$106.62	$106.60	$106.60
Purchase #4	$177.79	10.585%	$196.6091	$196.61	$196.60	$196.60
Purchase #5	$117.26	5.245%	$123.4103	$123.41	$123.40	$123.40
Purchase #6	$113.80	13.612%	$129.2905	$129.29	$129.30	$129.30
Purchase #7	$151.28	10.168%	$166.6622	$166.66	$166.65	$166.70
7 purchase totals =	$1,037.15		$1,147.0166	$1,147.01	$1,146.95	$1,147.00