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	$74.97	3.756%	$77.7859	$77.79	$77.80	$77.80
Purchase #2	$164.61	4.848%	$172.5903	$172.59	$172.60	$172.60
Purchase #3	$99.94	5.661%	$105.5976	$105.60	$105.60	$105.60
Purchase #4	$172.57	6.714%	$184.1563	$184.16	$184.15	$184.20
Purchase #5	$191.88	4.344%	$200.2153	$200.22	$200.20	$200.20
Purchase #6	$110.65	3.553%	$114.5814	$114.58	$114.60	$114.60
Purchase #7	$93.85	5.219%	$98.748	$98.75	$98.75	$98.70
7 purchase totals =	$908.47		$953.6748	$953.69	$953.70	$953.70