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	$196.47	10.105%	$216.3233	$216.32	$216.30	$216.30
Purchase #2	$57.62	8.298%	$62.4013	$62.40	$62.40	$62.40
Purchase #3	$111.51	11.182%	$123.979	$123.98	$124.00	$124.00
Purchase #4	$230.32	4.153%	$239.8852	$239.89	$239.90	$239.90
Purchase #5	$185.36	6.504%	$197.4158	$197.42	$197.40	$197.40
Purchase #6	$200.33	13.448%	$227.2704	$227.27	$227.25	$227.30
Purchase #7	$117.34	13.128%	$132.7444	$132.74	$132.75	$132.70
7 purchase totals =	$1,098.95		$1,200.0194	$1,200.02	$1,200.00	$1,200.00