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	$219.78	6.433%	$233.9184	$233.92	$233.90	$233.90
Purchase #2	$59.87	11.640%	$66.8389	$66.84	$66.85	$66.80
Purchase #3	$145.46	5.502%	$153.4632	$153.46	$153.45	$153.50
Purchase #4	$111.26	9.558%	$121.8942	$121.89	$121.90	$121.90
Purchase #5	$115.86	6.606%	$123.5137	$123.51	$123.50	$123.50
Purchase #6	$5.42	3.438%	$5.6063	$5.61	$5.60	$5.60
Purchase #7	$126.32	12.694%	$142.3551	$142.36	$142.35	$142.40
7 purchase totals =	$783.97		$847.5898	$847.59	$847.55	$847.60