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	$116.34	9.680%	$127.6017	$127.60	$127.60	$127.60
Purchase #2	$186.61	5.255%	$196.4164	$196.42	$196.40	$196.40
Purchase #3	$209.93	8.396%	$227.5557	$227.56	$227.55	$227.60
Purchase #4	$231.29	5.191%	$243.2963	$243.30	$243.30	$243.30
Purchase #5	$137.83	5.183%	$144.9737	$144.97	$144.95	$145.00
Purchase #6	$228.59	5.705%	$241.6311	$241.63	$241.65	$241.60
Purchase #7	$196.79	13.186%	$222.7387	$222.74	$222.75	$222.70
7 purchase totals =	$1,307.38		$1,404.2136	$1,404.22	$1,404.20	$1,404.20