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	$157.97	11.181%	$175.6326	$175.63	$175.65	$175.60
Purchase #2	$90.95	3.851%	$94.4525	$94.45	$94.45	$94.50
Purchase #3	$94.50	9.838%	$103.7969	$103.80	$103.80	$103.80
Purchase #4	$52.40	8.670%	$56.9431	$56.94	$56.95	$56.90
Purchase #5	$65.27	6.602%	$69.5791	$69.58	$69.60	$69.60
Purchase #6	$106.30	4.291%	$110.8613	$110.86	$110.85	$110.90
Purchase #7	$165.25	12.284%	$185.5493	$185.55	$185.55	$185.50
7 purchase totals =	$732.64		$796.8148	$796.81	$796.85	$796.80