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	$99.55	3.608%	$103.1418	$103.14	$103.15	$103.10
Purchase #2	$170.79	12.386%	$191.944	$191.94	$191.95	$191.90
Purchase #3	$134.40	4.603%	$140.5864	$140.59	$140.60	$140.60
Purchase #4	$49.75	8.439%	$53.9484	$53.95	$53.95	$53.90
Purchase #5	$127.34	5.569%	$134.4316	$134.43	$134.45	$134.40
Purchase #6	$144.76	12.159%	$162.3614	$162.36	$162.35	$162.40
Purchase #7	$237.85	13.184%	$269.2081	$269.21	$269.20	$269.20
7 purchase totals =	$964.44		$1,055.6217	$1,055.62	$1,055.65	$1,055.50