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	$146.96	10.128%	$161.8441	$161.84	$161.85	$161.80
Purchase #2	$104.67	7.445%	$112.4627	$112.46	$112.45	$112.50
Purchase #3	$23.56	7.175%	$25.2504	$25.25	$25.25	$25.30
Purchase #4	$90.28	8.560%	$98.008	$98.01	$98.00	$98.00
Purchase #5	$109.72	4.571%	$114.7353	$114.74	$114.75	$114.70
Purchase #6	$91.72	12.710%	$103.3776	$103.38	$103.40	$103.40
Purchase #7	$171.39	5.530%	$180.8679	$180.87	$180.85	$180.90
7 purchase totals =	$738.30		$796.5460	$796.55	$796.55	$796.60