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	$222.95	12.392%	$250.578	$250.58	$250.60	$250.60
Purchase #2	$47.98	3.540%	$49.6785	$49.68	$49.70	$49.70
Purchase #3	$103.71	8.431%	$112.4538	$112.45	$112.45	$112.50
Purchase #4	$194.89	13.317%	$220.8435	$220.84	$220.85	$220.80
Purchase #5	$174.78	6.691%	$186.4745	$186.47	$186.45	$186.50
Purchase #6	$106.26	10.615%	$117.5395	$117.54	$117.55	$117.50
Purchase #7	$87.85	3.139%	$90.6076	$90.61	$90.60	$90.60
7 purchase totals =	$938.42		$1,028.1754	$1,028.17	$1,028.20	$1,028.20